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CHEMICAL  EXPERIMENTS 


PREPARED  TO  ACCOMPANY  REMSEN'S  "INTRO- 
DUCTION TO  THE  STUDY  OF  CHEMISTRY" 


BY 
IRA   REMSEN 

Professor  of  Chemistry  in  the  Johns  Hopkins  University 
AND 

WYATT  W.   RANDALL 

Associate  in  Ciiemistry  in  the  Johns  Hopkins  University 


NEW  YORK 
HENRY  HOLT  &  COMPANY 

1895 


Copyright,  1895, 

BY 
HENRY  HOLT  &  CO. 


ROBERT  DRUMMOND,  ELECTROTYPBR  AND  PRINTER,   NEW  YORK. 


PREFACE. 

THIS  book  lias  been  prepared  for  use  as  a  laboratory 
guide  to  accompany  the  study  of  Remsen's  "  Intro- 
duction to  the  Study  of  Chemistry."  The  experiments 
included  in  the  course  are  essentially  those  in  the  last 
edition  of  the  "Introduction."  Minor  changes  have 
been  made  in  many  of  them ;  essential  changes  in  a 
few.  If  the  directions  are  followed,  the  average  stu- 
dent will  experience  no  difficulty  in  carrying  them  out 
successfully. 

The  numbering  of  the  experiments  in  the  "  Intro- 
duction" has  been  followed  in  this  book;  additional 
experiments  have  been  inserted,  and  designated  as 
"  15a,"  "  25a,"  "  256,"  etc.  In  the  latter  class  will  be 
found  a  small  number  of  experiments  not  contained  in 
the  "Introduction,"  but  which  have  been  inserted 
here  in  accordance  with  the  recommendation  of  the 
Committee  on  Secondary  School  Studies,  whose  report 
was  published  by  the  United  States  Bureau  of  Edu- 
cation in  1893.  As  many  of  the  experiments  there 
recommended  have  been  inserted  as  seemed  to  the 
authors  to  be  of  advantage  to  the  student  following 
this  course,  the  time  at  disposal  and  the  facilities  of 
the  average  laboratory  being  taken  into  account. 

In  some  cases  it  may  be  that  in  laboratories  not 
completely  equipped  fairly  satisfactory  results  may  be 
obtained  with  simpler  apparatus.  The  effort  has, 
however,  been  made  in  this  book  to  omit  everything 

iii 


iv  PREFACE. 

which  does  not  serve  to  insure  the  success  of  the  ex- 
perimental work. 

It  has  seemed  best  to  include  all  the  experiments 
contained  in  Eemsen's  "  Introduction  to  the  Study  of 
Chemistry."  There  are,  however,  a  number  of  these 
which  are  not  suited  to  general  laboratory  practice : 
they  should  be  reserved  for  the  ]ecture-room,  or  at 
most  performed  only  with  the  assistance  of  a  compe- 
tent teacher.  In  this  University  the  experiments  in 
the  "  Introduction  "  usually  omitted  from  the  general 
laboratory  course  are  Nos.  4,  25,  26,  28,  34,  43,  45, 
47,  48,  56. 

As  many  as  possible  of  those  omitted  should  be 
performed  by  the  teacher  in  the  presence  of  the  class  ; 
and  the  points  of  importance  should  be  drawn  out  by 
questions.  Afterwards  the  pupils  should  write  a  full 
account  of  what  they  have  seen,  and  draw  such  con- 
clusions as  the  experiments  may  lead  to. 

THE  AUTHORS. 
BALTIMORE,  September,  1895. 


LIST  OP  EXPERIMENTS. 

1.  Physical  and  chemical  change. 

2.  Heat 
3 

4.  The  electric  current  and  chemical  change. 

5.  Manipulation  of  gases. 

6.  "  "       " 

7.  Mechanical  mixture  :  recognition  of  ingredients. 

8.  "  separation    "          " 

Q  K                               <  (                                    «                      It                     if 

10.  conversion  by  heat  into  a  chemical  com- 

pound. 

11.  Contact  and  chemical  change. 
12. 

13. 
14. 

15.  "         "          "  " 
15a.  Oxygen  :  from  mercuric  oxide. 

16.  "  "    potassium  chlorate. 

17.  "  "    manganese  dioxide. 

18.  "    potassium  chlorate  and  manganese  dioxide. 

19.  Physical  properties  of  oxygen. 

20.  Action  of  oxygen  at  ordinary  temperature. 

21.  "       "         "       on  sulphur  at  high  temperatures. 

22.  "        "         "        "  carbon     "     "  «« 

23.  "       "        "        "  phosphorus  ".  " 

24.  "       "        "        "  steel  at  "            " 

25.  Absorption  of  oxygen  by  iron  at    "  " 
25a.  Oxidation  in  the  air. 

256.  "          "     "     " 

26.  Hydrogen:  electrolysis  of  water. 

27.  "  action  of  sodium  on  water. 

28.  "  "       "   iron 

29.  "  "       '*   zinc  on  acids. 

30.  Products  of  the  action  of  zinc  on  acids. 


vi  LIST  OF  EXPERIMENTS. 

31.  Hydrogen:  purification. 

32.  "  physical  properties. 

33.  "  "               " 

34.  "  "               " 

35.  burning  in  air. 

36.  does  not  support  combustion. 

37.  Water  included  in  porous  substances. 

38.  "      of  crystallization. 

39.  "       "  •«  • 

40.  "       " 

41.  Efflorescent  compounds. 

42.  Deliquescent        " 

43.  Water  composed  of  oxygen  and  hydrogen. 

44.  "      produced  by  the  burning  of  hydrogen  in  air. 

45.  Electrolytic  gas. 

46.  Action  of  hydrogen  on  hot  copper  oxide. 

47.  Oxyhydrogen  blowpipe. 

48.  "  "           lime-light. 

49.  Distillation  of  water. 
49a.  Water  as  a  solvent. 

496.  Solution  with  and  without  permanent  chemical  change. 

49c.  Solution  aids  chemical  action. 

49dr 

50.  Weight  of  oxygen  in  a  given  weight  of  potassium  chlorate. 

51.  Atomic  weight  of  zinc. 

52.  Action  of  sulphuric  acid  on  salt. 

53.  Oxygen  from  manganese  dioxide  and  sulphuric  acid. 

54.  Chlorine. 

55.  Action  of  chlorine  on  compounds  of  hydrogen. 

56.  "       " 

57.  Direct  combination  of  chlorine  and  hydrogen. 

58.  Hydrochloric  acid. 

59.  Preparation  of  potassium  chlorate. 

60.  "  *'  bleaching-powder. 

61.  Neutralization  :  quantitative  relations. 

62.  "  formation  of  salts. 

63.  Air:  proportion  of  oxygen. 

64.  "     nitrogen. 

65.  "     water-vapor. 

66.  "    carbon  dioxide. 

67.  "    removal  of  carbon  dioxide. 


LIST  OF  EXPERIMENTS.  VU 

68.  Air  :  formation  of  carbon  dioxide. 

69.  "    removal  of  water- vapor. 

70.  Ammonia. 
71. 

72.  "  acts  as  a  base. 

73.  Direct  combination  of  ammonia  with  volatile  acids. 

74.  Nitric  acid  :  preparation. 

75.  "         "       concentration. 

76.  "        "       as  an  oxidizing  agent. 

r*y  tt            t<           <(      a           K                   <« 

78.  "        "       "    " 

79.  "        "••-',  formation  of  nitrates 

80.  Action  of  nitrates  under  the  influence  of  heat. 

81.  Solubility  of  nitrates  in  water. 

82.  Nitric  acid  reduced  to  ammonia. 

83.  Nitrous  acid  and  nitrites. 

84.  Nitrous  oxide. 

85.  Nitric  oxide  :  preparation. 

86.  "  "       properties. 
86#.  "         "       analysis. 

87.  Carbon  :  use  of  bone-black  for  filters. 

88.  "        direct  union  with  oxygen. 

89.  "        action  upon  metallic  oxides. 
90. 

91.  Carbon  dioxide :  formation  in  the  lungs. 

92.  "  "         preparation  from  carbonates. 

93.  "  '*,-'  properties. 

94.  Formation  of  carbonates. 
95. 

96.  Solution  of  calcium  carbonate. 

97.  Carbon  monoxide  :  preparation. 

98.  "  "           as  a  reducing  agent. 

99.  Oxygen  burning  in  an  atmosphere  of  coal-gas. 

100.  Flame. 

101.  Reduction  with  the  aid  of  the  blowpipe. 

102.  Oxidation     "       •«««'" 

103.  Bromine. 

104.  Action  of  sulphuric  acid  on  bromides. 

105.  Iodine. 

106.  Solvents  for  iodine. 

107.  Iodine  and  starch. 


LIST  OF  EXPERIMENTS. 

108.  Action  of  sulphuric  acid  on  iodides. 

109.  Hydrofluoric  acid. 

110.  Distillation  of  sulphur. 

111.  Crystallization  of  molten  sulphur. 

"  sulphur  from  solution. 

113.  Direct  union  of  sulphur  and  metals. 

114.  Hydrogen  sulphide. 

115.  Insoluble  sulphides. 

116.  Sulphur  dioxide. 

H7-  "        as  a  bleaching  agent. 

118.  Reaction  between  phosphorus  and  iodine. 

119.  Phosphine. 

120.  Arsine. 

121.  Arsenic  from  arsine. 

122.  Action  of  carbon  on  arsenic  trioxide. 

123.  Antimony  and  arsenic. 

124.  Stibine. 

125.  Antimony  from  stibine. 

126.  Bismuth. 

127.  Borax  and  boric  acid. 

128.  Reactions  of  chlorides. 

129.  Preparation  of  hydroxides. 

130.  Reactions      "          " 
131. 

132.  "  "  sulphides. 

133.  "  «  nitrates. 

134.  Preparation  of  sulphates. 
135. 

136.  Reactions       "         " 

137.  Reduction      "        " 

138.  Reactions  of  carbonates. 

139.  Preparation  of  silicates. 

140.  Silicic  acid. 

141.  Potassium  carbonate  in  wood-ashes. 
141a.  Action  of  potassium  on  water. 

142.  Potassium  iodide. 

143.  Preparation  of  potassium  hydroxide. 

144.  Nitre  as  an  oxidizing  agent. 

145.  Sodium  carbonate  :  Solvay  process, 

146.  Volatility  of  ammonium  salts. 

147.  Ammonium  sulphide. 


LIST  OF  EXPERIMENTS.  ix 

148.  Insoluble  potassium  salts. 

149.  Flame  reactions. 

150.  Calcium  chloride. 

151.  "       hydroxide. 
152. 

153.  Plaster  of  Paris. 

154.  Action  of  ammonium  carbonate  on  calcium  sulphate. 

155.  Calcium  phosphate. 

156.  Zinc  oxide. 

157.  Insoluble  salts  of  zinc. 

158.  Precipitation  of  metallic  copper. 

159.  Copper  hydroxide. 

160.  Copper  sulphide. 

160&.  Precipitation  of  mercury. 

161.  Analysis  of  coin-silver. 

162.  Halogen  salts  of  silver. 

163.  Precipitation  of  metallic  silver. 

164.  Insoluble  salts  of  silver. 
164$.  Solvents  for  aluminium. 

165.  Aluminium  hydroxide. 

166.  Alum. 

167.  Aluminium  hydroxide  precipitated  by  soluble  carbonates. 

168.  "  "  •»,.'•"      sulphides. 

169.  Precipitation  of  metallic  lead. 

170.  Action  of  water  and  air  on  metallic  lead. 

171.  Oxides  of  lead. 

172.  Lead  peroxide  as  an  oxidizing  agent. 

173.  Action  of  sulphuric  acid  on  lead  peroxide. 

174.  Lead  chloride. 

175.  Stannous  chloride. 

176.  Stannic 

177.  Antimony  and  tin. 

178.  Analysis  of  solder. 

179.  "       "  bronze. 

180.  Ferrous  and  ferric  hydroxides. 

181.  Potassium  permanganate  :  preparation. 

182.  as  an  oxidizing  agent. 

183.  "          chromate. 

184.  "          dichromate. 

185.  Conversion  of  dichromates  into  chromates. 

186.  Salts  of  chromic  acid  as  oxidizing  agents. 


X  LIST  OF  EXPERIMENTS. 

187.  Insoluble  chromates. 

188.  Chromium  as  a  base -forming  element. 

189.  Fermentation  of  glucose. 

190.  Aldehyde. 

191.  Soap. 

192.  Hard  water. 
193. 

194.  Tannic  acid. 

How  to  analyze  substances. 

Examples  for  practice. 

List  of  substances  for  examination. 

195.  Study  of  Class    I. 

196.  "      "      "      II. 

197.  "      "      "    HI.:  Aluminium. 

198.  "      "      "     "       Chromium. 

199.  "       "      "     "       Iron. 

200.  "      "      "     "       Zinc. 

201.  "       "      "     "       Manganese. 

202.  "      "      "      " 

203.  "      «      "    IV.:   Calcium. 

204.  "      "      "      "       Barium. 

205.  "      "      "      V.:   Magnesium. 

206.  '*      "      "VI. 


Symbols  and  Atomic  Weights  of  the  Elements. 
Weights  and  Measures. 


CHEMICAL  EXPERIMENTS. 

GENERAL  LABORATORY  DIRECTIONS. 

1.  Neatness  is  one  of  the  first  conditions  of  success 
in  chemical  work.     Keep  your  laboratory  desk,  as  well 
as  all  your  apparatus,  clean. 

2.  Provide  yourself  with  a  working-apron  to  protect 
your  clothing. 

3.  Always  have  a  decent  towel  available. 

4.  In  observing  use  your  own  eyes. 

5.  In  describing  experiments  use  your  own  ivords. 

6.  In  thinking  over  the  results  use  your  own  mind. 

1.  An  experiment  should  be  repeated  as  many  times 
as  may  be  necessary  to  secure  accurate  work. 

8.  If  the  results  obtained  are  not  those  which  you 
have  been  led  to  expect,  try  in  every  way  you  can 
think   of  to  find  out  what  the  matter  is.     See  first 
whether  you  have  worked  exactly  as  directed. 

9.  After  an  experiment  is  finished,   write  in  your 
note-book  in  the  laboratory  an  account  of  what  you 
have  done.     Remember  that  this  account  is  not  in- 
tended to  be  a  series  of  mere  short-hand  notes  of  your 
work.     Laboratory  work,  to  be  of  value,  must  consist 
of   two  parts :  (1)  the  actual  performance  of  certain 
experiments,  and  (2)  the  preparation  of  a  concise  and 
yet  accurate  record  of  the  method  employed  and  the 
results  obtained.     If  you  are  able  to  draw  any  con- 

1 


2  GENERAL  LABORATORY  DIRECTIONS. 

elusions  from  what  you  have  seen,  state  what  these 
conclusions  are.  Write  the  description  accurately 
and  in  as  good  English  as  possible.  Do  not  use  ab- 
breviations. In  referring  to  chemical  substances  do 
not  use  simply  the  name,  but  the  full  name  with  the 
symbol  after  it.  Thus,  potassium  chlorate,  KC1O3; 
hydrochloric  acid,  HC1.  Further,  in  speaking  of 
chemical  substances  do  not  use  symbols.  For  exam- 
ple, do  not  say,  "  I  poured  some  H2SO4  into  an  H2O 
solution  of  BaCl2,"  but  say  in  English  what  you  did. 

10.  After  you  have  written  an  account  of  an  experi- 
ment have  it  examined  by  the  teacher  before  you  go 
on  to  the  next  one. 

11.  Always  read  before  and  after  an  experiment  or 
a  set  of   experiments  that  part   of   the  text-book  in 
which  the  experiment  or  experiments  are  referred  to, 
and  keep  reviewing  constantly. 

12.  If  an  experiment  not  included  in  your  course  is 
performed  by  you  or  by  your  teacher,  write  an  accu- 
rate account  of  it  as  if  you  had  yourself  performed  it, 
but  do  not  make  any  statement  without  entirely  satis- 
factory reasons  for  making  it. 

13.  In  working  with  gases  see  that  all  the  joints  of 
your  apparatus  are  tight. 

14.  In  case  of  fire,  a  moist  towel  thrown  over  the 
flame  will  generally  be  sufficient  to  extinguish  it. 

15.  Acid  wounds  should  first  be  washed  out,  and  a 
paste  of  sodium  bicarbonate  and  water  then  applied. 

16.  Burns  should  be  treated  with  a  paste  of  sodium 
bicarbonate  and  water. 


PHYSICAL   CHANGE;   CHEMICAL   CHANGE.          3 

PHYSICAL  CHANGE;    CHEMICAL  CHANGE. 
EXPERIMENT  1. 

Platinum  wire  ;  magnesium  ribbon  or  wire. 

1.  Hold  a  piece  of  platinum  wire  in  the  flame  of  the 
laboratory  burner  or  of  a  spirit-lamp  for  a  moment ; 
then  remove  it  and  hold  it  in  the  air  for  a  few  ino 
ments. 

What  kind  of  change  did  it  undergo  in  the  flame  ? 

2.  Hold  a  piece  of  magnesium  ribbon  or  wire  in  the 
flame  by  means  of  a  pair  of  pincers :  what  kind  of 
change  takes  place  ?     Give  reasons  for  your  conclu- 
sions. 

3.  Mention  some  phenomena  familiar  to  you  that 
further  illustrate  these  two  kinds  of  change. 

HEAT  AND   CHEMICAL  CHANGE. 
EXPERIMENT  2. 

Test-tube  ;  sugar. 

In  a  clean  dry  test-tube  put  enough  white  sugar  to 
make  a  layer  4  to  J  inch  thick.  Holjl 
the  tube  in  the  flame  of  a  spirit-lamp 
or  of  a  laboratory  burner  as  shown  in 
Fig.  1,  until  no  further  change  takes 
place.  Meantime  what  have  you  no- 
ticed? 

What  do  you  see  on  the  sides  of  the 
tube? 

What  is  the  color  and  taste  of  that 
which  remains  behind  ? 

Does  it  dissolve  in  water  ? 

Is  it  sugar  ?  Fl«- 


4     ELECTRIC  CURRENT  AND  CHEMICAL  CHANGE. 

EXPERIMENT  2— Continued. 

Is  the  change  which  has  taken  place  chemical  or 
physical  ?     Why  do  you  think  so  ? 
What  caused  the  change  ? 

EXPERIMENT  3. 

Arsenic-tube*  ;  mercuric  oxide  ;  splinter  of  wood. 

Into  a  clean,  dry  arsenic-tube  put  enough  red  oxide 
of  mercury  (mercuric  oxide)  to  fill  the  bulb  three- 
fourths  full.  Heat  the  tube  as  in  Experiment  2. 

What  change  in  color  takes  place  ? 

What  is  deposited  on  the  sides  of  the  tube? 

2.  During  the  heating  insert  into  the  tube  a  splin- 
ter of  wood  with  a  spark  on  the  end.     What  follows? 

Take  it  out  and  put  it  back  a  few  times. 
Is  there  any  difference  between  the  burning  in  the 
tube  and  put  of  it  ?     What  difference  ? 

3.  Continue  the  heating  until  the  red  substance  has 
all  disappeared. 

How  do  you  know  that  the  red  substance  which  you 
put  into  the  tube  has  been  changed  ? 
Is  the  change  chemical  or  physical  ? 
What  caused  the  change  ? 

THE  ELECTRIC  CURRENT  AND  CHEMICAL 
CHANGE. 

EXPERIMENT  4. 

2  cells  of  Grove  or  Bunsen  type ;  platinum-foil ;  copper  (or  platinum) 
wire  ;  sulphuric  acid  ;  wood  splinter  ;  apparatus  shown  in  Fig.  2. 

1.  To  the  ends  of  the  copper  (or  platinum)  wires 
connected  with  two  cells  of  a  Grove's  or  Bunsen's 

*  Such  a  tube  is  also  called  an  ignition-tube  or  mattrass. 


ELECTRIC  CURRENT  AND  CHEMICAL  CHANGE.      5 


EXPERIMENT  4—  Continued. 

battery  fasten  small  platinum  plates,  say  25  mm.  (1 
inch)  long  by  12  mm.  (J-  inch)  wide.  Insert  these  plat- 
inum electrodes  into  water  contained  in  a  small  shal- 
low glass  vessel  about  15  cm.  (6  inches)  wide  by  7  to  8 
cm.  (3  inches)  deep,  taking  care  to  keep  them  separated 
from  one  another.  No  action  will  take  place,  for  the 
reason,  as  has  been  shown,  that  water  will  not  conduct 
the  current,  and  hence  when  the  platinum  electrodes 
are  kept  apart  there  really  is  no  current.  By  adding 
to  the  water  about  one-tenth  its  own  volume  of  strong 
sulphuric  acid  we  give  it  the  power  to  convey  the  cur- 
rent. It  will  then  be  observed  that  bubbles  rise  from 
each  of  the  platinum  plates.  In  order  to  collect  them 
an  apparatus  like  that  shown  in  Fig.  2  may  be  used. 

h  and  o  represent  glass  tubes 
which  may  conveniently  be  about 
30  cm.  (1  foot)  long  and  25  mm. 
(1  inch)  in  internal  diameter.  They 
are  first  filled  with  the  water  con- 
taining one-tenth  its  volume  of 
sulphuric  acid  and  are  then  placed 
with  the  mouth  under  water  in 
the  vessel  A.  The  platinum  elec- 
trodes are  now  brought  beneath 
the  inverted  tubes.  The  bubbles 
which  rise  from  them  will  pass  up- 
ward in  the  tubes  and  the  water 
will  be  displaced.  FlG  2 

2.  Gradually  the  water  will  be  completely  forced 
out  of  one  of  the  tubes,  while  the  other  is  still  half-full. 
The  substance  thus  collected  in  each  tube  is  an  in- 
visible gas.  After  the  first  tube  is  full  of  gas,  place 


G 


MANIPULATION  OF  GASES. 


EXPERIMENT  4 — Continued. 

the  thumb  over  its  mouth  and  remove  the  tube.  Turn 
it  mouth-upward  and  at  once  apply  a  lighted  match 
to  it. 

What  takes  place  ?  Was  the  gas  in  the  tube  ordi- 
nary air?  Does  a  tube  full  of  air  act  in  the  same 
way?  Try  it. 

3.  In  the  meantime  the  second  tube  will  have  be- 
come filled  with  gas.  Remove  this  tube  in  the  same 
way  and  insert  a  thin  piece  of  wood  with  a  spark  on 
it.  What  do  you  observe  ?  Is  it  air  ?  In  what  ex- 
periment already  performed  have  you  observed  some- 
thing very  like  this  ? 

MANIPULATION  OF  GASES. 
EXPERIMENT  5. 

Pneumatic  trough  ;  cylinder  or  test-tube. 

1.  Fill  a  glass  cylinder  or  test-tube  with   water ; 


FIG.  3. 


close  the  mouth  with  a  glass  plate  or  with  the  thumb  ; 
invert  the  tube,  and  put  the  mouth  under  water  in  the 


MECHANICAL  MIXTURE.  7 

EXPERIMENT  5— Continued. 

trough.  The  water  stays  in  the  tube  after  the  glass 
plate  or  thumb  is  removed. — Why  ? 

2.  Now  take  a  piece  of  glass  or  rubber  tubing  ;  put 
one  end  under  the  mouth  of  the  inverted  tube,  and 
blow  gently  through  the  other  end.  What  happens  ? 
What  becomes  of  the  water  which  was  in  the  tube  ? 
Why? 

EXPERIMENT  6. 

Pneumatic  trough;  cylinders  or  test-tubes. 

Fill  a  cylinder  or  test-tube  with  water  and  invert  it 
in  the  trough,  as  in  Experiment  5.  Introduce  a  sec- 
ond cylinder  or  test-tube, 
full  of  air,  mouth-downward 
in  the  water  in  the  trough  ; 
bring  its  mouth  below  that 
of  the  first  cylinder,  and. 
then  incline  it  so  that  the 
air  passes  from  one  vessel 
to  the  other.  —  See  Fig.  4.  FIG.  4. 

Why  does  the  air  pass  to  the  higher  vessel?  If  the 
second  cylinder  had  been  filled  with  an  oil  lighter 
than  water,  could  it  have  been  transferred  in  the  same 
way? 

MECHANICAL  MIXTURE. 
EXPERIMENT  7. 

Powdered  roll-sulphur;  fine  iron-filings;  magnifying-glass  or  small 
microscope. 

Mix  two  or  three  grams  of  powdered  roll-sulphur 
and  an  equal  weight  of  very  fine  iron-filings  in  a  small 
dry  mortar.  Examine  a  little  of  the  mixture  with  a 
microscope  or  a  magnifying-glass. 


8  MECHANICAL  MIXTURE. 

EXPERIMENT  7—  Continued. 

Can  you  distinguish  the  particles  of  sulphur  and 
those  of  iron  ? 

EXPERIMENT  8. 

Mixture  obtained  in  last  Experiment;  small  magnet. 
Pass  a  small  magnet  over  the  mixture. 
Are  particles  of  iron  drawn  out  of  the  mixture  ? 
Has  chemical  action  taken  place  between  the  sul- 
phur and  the  iron-filings  ?     How  do  you  know  ? 

EXPERIMENT  9. 

Bisulphide  of  carbon  ;  powdered  roll-sulphur  ;  dry  test-tubes  ;  iron- 
filings  ;  filter;  good-sized  watch-glass. 

1.  Pour  two  or  three  cubic  centimeters  of  disulphide 
of  carbon  *  on  about  a  gram  of  powdered  roll-sulphur 
in  a  dry  test-tube  and  shake  the  tube. 

Does  the  sulphur  dissolve  ? 

2.  In  a  second  tube  treat  a  little  iron-filings  in  the 
same  way. 

Does  the  iron  dissolve  ? 

3.  Now  treat  about  half  of  the  mixture  prepared  in 
Experiment  7  with  three  or  four  times  its  bulk  of 
disulphide  of  carbon.    After  shaking  thoroughly,  pour 
the  contents  of  the  test-tube  upon  a  dry  filter ;  f  catch 

*  Disulphide  of  carbon  is  a  very  volatile,  inflammable  liquid.  In 
working  with  it  great  care  should  be  taken  to  keep  it  away  from  all 
flames.  You  should  never  heat  it,  either  for  the  purpose  of  aiding 
solution  or  to  evaporate  it. 

f  A  word  about  filters,  before  going  further:  If  your  filter-paper 
is  in  the  form  of  sheets,  cut  some  of  it  into  circular  pieces  of  a 
diameter  about  l£  times  that  of  the  funnel  you  intend  to  use  it  with. 
Take  one  of  these  pieces,  fold  it  twice,  at  right  angles,  so  that  it  forms 
a  quadrant,  open  it  out  into  a  hollow  cone  and  fit  this  into  the  fun- 
nel. The  funnel  should  be  dry  and  clean.  If  the  funnel  is  of  the 


MECHANICAL  MIXTURE  CONVERTED  BY  HEAT.      9 

EXPERIMENT  9— Continued. 

the  filtrate  upon  a  watch-glass.     What  is  left  in  the 
filter? 

Is  it  iron  ? 

4.  After  the  liquid  has  evaporated  examine  what  is 
left  on  the  watch-glass. 

Is  it  sulphur  ? 

A  MECHANICAL   MIXTURE   CONVERTED    INTO 
A  CHEMICAL   COMPOUND   BY   HEAT. 

EXPERIMENT  10. 

Powdered  roll- sulphur  ;  filings  of  wrought  iron  or  powdered  iron  ; 
dry  test-tube;  small  dry  mortar;  magnifying-glass  ;  carbon 
disulphide  ;  magnet ;  dilute  hydrochloric  acid. 

1.  Mix  three  grams  of  finely-powdered  roll-sulphur 
with  the  same  weight  of  fine  iron-filings.    Put  the  mix- 
ture in  a  dry  test-tube.     Heat  the  bottom  of  the  tube 
strongly  and  note  the  changes.     Does  a  glow  spread 
upwards  through  the  contents  of  the  tube  ? 

Is  there  any  evidence  that  heat  is  caused  by  the 
change  ? 

2.  After  the  action  is  over  and  the  tube  has  cooled 
down,  break  it  and  put  the  contents  in  a  small  dry 
m  ortar. 


right  shape  the  paper  will  fit  the  walls  close,  with  three  thicknesses 
of  paper  on  one  side  and  one  on  the  other. 

Now  with  the  paper  pressed  down  into  place  wet  the  filter  with  the 
liquid  which  is  to  be  filtered  through  it.  As  we  generally  work  with 
aqueous  solutions,  this  will  of  course  generally  be  water  ;  in  Experi- 
ment 9,  however,  carbon  disulphide  must  be  used.  Once  wet,  the 
paper  will  stay  in  place. 

Two  papers,  one  inside  the  other,  will  filter  more  rapidly  and  per- 
fectly than  one  alone.  A  knowledge  of  this  fact  is  often  of  value. 


10  CONTACT  AND   CHEMICAL   CHANGE. 

EXPERIMENT  10—  Continued. 

Does  the  mass  look  like  the  mixture  of  sulphur  and 
iron  with  which  you  started? 

3.  Examine  with  a  microscope  or  magnifying-glass  ; 
with  carbon  disulphide ;  with  a  magnet. 

Treat  a  little  of  the  mass  with  dilute  hydrochloric 
acid  and  warm  slightly.  What  takes  place?  Treat  a 
little  of  a  mixture  of  iron  and  sulphur  in  the  same 
way.  Is  the  action  the  same  ?  Are  the  products  the 
same? 

Compare  your  observations  with  those  made  on  the 
mixture  used  in  the  preceding  experiment. 

What  conclusions  does  this  experiment  lead  you  to  ? 

CONTACT   AND   CHEMICAL   CHANGE. 
EXPERIMENT  11. 

Small  piece  of  calc-sparor  marble  ;  ignition-tube  ;  dilute  hydrochloric 
acid ;  small  porcelain  evaporating- dish  ;  water-bath  ;  test-tube. 

1.  Examine  a  piece  of  calc-spar  or  of  marble.  No- 
tice whether  it  is  hard  or  soft.  Heat  a  small  piece  in 
a  glass  tube  such  as  was  used  in  Experiment  3. 

Does  it  change  in  any  way  ? 

Does  it  dissolve  in  water? 

[In  order  to  learn  whether  a  substance  is  soluble  in 
water  proceed  as  follows  :  Put  a  piece  about  the  size 
of  a  pea  in  a  test-tube  with  distilled  water.  Thoroughly 
shake,  and  then,  as  heating  usually  aids  solution,  boil. 
Now  pour  off  a  few  drops  of  the  liquid  on  a  piece  of 
platinum-foil  or  a  watch-glass,  and  by  gently  heating 
cause  the  water  to  pass  off  as  steam.  If  there  is  any- 
thing solid  in  solution  there  will  be  something  solid 


CONTACT  AND  CHEMICAL  CHANGE.  11 

EXPERIMENT  11 — Continued. 

left  on  the  platinum-fail  or  watch-glass.     If  not,  there 
will  be  nothing  left.] 

2.  Knowing  now  the  general  properties  of  the  calc- 
spar  or  marble  you  will  be  able  to  determine  whether 
it  is  changed  or  not.     Treat  a  small  piece  with  dilute 
hydrochloric  acid  in  a  test-tube. 

What  takes  place  ? 

3.  After  the  action  has  continued  for  about  half  a 
minute  insert  a  lighted  match  in  the  upper  part  of  the 
tube. 

Does  the  match  continue  to  burn  ? 
Does  the  substance  in  the  tube  burn  ? 
Is  the  invisible  substance  in  the  upper  part  of  the 
tube  ordinary  air  ? 
How  do  you  know  ? 
Does  the  solid  substance  disappear? 

4.  In  order  to  tell  whether  it  has  been  changed 
chemically  the  hydrochloric  acid  must  be  got  rid  of. 
This  can  be  done  by  boiling 

it,  when  it  passes  off  in  the 
form  of  vapor,  just  as  water 
does,  and  then  whatever  is  in 
solution  will  remain  behind. 
For  this  purpose  put  the  solu- 
tion in  a  small,  clean  porcelain 
evaporating-dish,  and  put  this 
on  a  vessel  containing  boiling 
water,  or  a  water-bath.  The 
operation  should  be  carried 

-,  i         -,  FIG.  5. 

on  under  a  hood  or,  at  any 

rate,  in  a  place  where  there  is  a  good  draught,  so  that 

the  vapors  will  not  collect  in  the  working  room.    They 


12  CONTACT  AND  CHEMICAL  CHANGE. 

EXPERIMENT  II— Continued. 

are  not  poisonous,  but  they  are  annoying.     The  ar- 
rangement for  evaporating  is  illustrated  in  Fig.  5. 

5.  After  the  liquid  has  evaporated  and  the  substance 
in  the  evaporating-dish  is  dry,  examine  it  and  carefully 
compare  its  properties  with  those  of  the  substance 
which  was  put  into  the  test-tube. 

Is  it  the  same  substance  ? 

Is  it  hard  or  soft  ? 

Does  it  change  when  heated  in  an  ignition-tube  ? 

Is  there  an  appearance  of  bubbling  when  hydro- 
chloric acid  is  poured  on  it  ? 

Does  it  dissolve  in  water  ? 

Does  it  change  when  allowed  to  lie  in  contact  with 
the  air? 

EXPERIMENT  12. 

Test-tube ;   bit  of  copper ;   concentrated  nitric  acid ;    evaporating- 
dish;  water- bath. 

1.  Under  a  hood  bring  together  in  a  test-tube  a  bit 
of  copper,  half  the  size  of  a  ten-cent  piece,  and  a  little 
nitric  acid.*  Hold  the  mouth  of  the  tube  away  from 
your  face  and  do  not  inhale  the  vapors. 

What  is  the  appearance  of  the  vapors  given  off? 

What  is  the  appearance  of  the  liquid  in  the  tube  ? 

Does  the  copper  dissolve  ? 

If  it  does  not  dissolve  completely  add  a  few  drops 
more  of  the  acid.  Wait  until  no  more  action  takes 

*  The  acid  obtained  from  the  dealers  is  concentrated.  Use  great 
care  in  working  with  it,  as  its  action  on  the  skin  is  very  corrosive. 
For  ordinary  use  this  acid  should  be  diluted  by  mixing  it  with  four 
times  its  bulk  of  water.  Keep  two  bottles,  one  containing  concen- 
trated acid,  the  other  containing  dilute  acid.  In  this  experiment  use 
the  concentrated  acid. 


CONTACT  AND  CHEMICAL  CHANGE.  13 

EXPERIMENT  12—  Continued. 

place  and,  if  necessary,  add  a  few  drops  more  of  the 
acid. 

2.  Evaporate  the  solution,  as  in  the  preceding  Ex- 
periment, and  see  what  has  been  formed. 

What  are  the  properties  of  the  substance  found 
after  the  liquid  has  evaporated? 

Is  it  colored  ? 

Is  it  hard  or  soft  ? 

Does  it  change  when  heated  in  an  arsenic-tube  ? 

Is  it  soluble  in  water? 

Does  it  in  any  way  suggest  the  copper  with  which 
you  started  ? 

EXPERIMENT  13. 

Dilute  sulphuric  acid  ;   bit  of  granulated  zinc ;  evaporating-dish ; 
water-bath. 

1.  Try  the  action  of  dilute  sulphuric  acid  on  zinc 
in  a  test-tube.*     Apply  a  lighted  match  to  the  mouth 
of  the  tube. 

What  takes  place  ?  Have  you  had  to  do  with  this 
gas  before  ? 

2.  After  the  zinc  has  disappeared,  filter,  if  neces- 

*  In  experiments  made  in  test-tubes  the  quantities  to  be  used  are 
always  small.  In  this  experiment,  for  example,  use  one  or  two 
pieces  of  granulated  zinc  of  such  size  that  they  can  conveniently  be 
put  in  the  tube.  Then  add  enough  dilute  sulphuric  acid  to  cover 
the  zinc.  The  liquid  should  form  a  layer  from  one  to  two  inches  in 
height. 

The  sulphuric  acid  obtained  from  the  dealers  is  concentrated. 
Like  concentrated  nitric  acid,  it  should  be  used  with  great  care. 
Prepare  enough  dilute  acid  to  fill,  say,  a  4-oz.  bottle,  by  pouring  the 
concentrated  acid  slowly  into  four  times  its  bulk  of  water,  and  stir- 
ring thoroughly.  Label  the  bottle  dilute  sulphuric  acid.  Use  this 
in  Experiment  13. 


14  CONTACT  AND  CHEMICAL  CHANGE. 

EXPERIMENT  IS— Continued. 

sary,  and  evaporate  the  solution  as  before.  Carefully 
compare  the  properties  of  the  substance  left  behind 
with  those  of  zinc. 

What  differences  do  you  find  between  them  ? 

EXPERIMENT  14. 

Magnesium  ribbon  or  wire. 

Hold  the  end  of  a  piece  of  magnesium  ribbon  or 
wire  about  20  cm.  (8  inches)  long  in  a  flame  until  it 
takes  fire ;  then  hold  the  burning  substance  quietly 
over  a  piece  of  dark  paper,  so  that  the  light  white 
product  may  be  collected.  Compare  the  properties 
of  this  white  product  with  those  of  the  magnesium  : 
are  they  different? 

What  substances  have  taken  part  in  the  formation 
of  this  product  ? 

EXPERIMENT  15. 

Dry  flask  of  4-oz.  capacity  ;  bit  of  granulated  tin  or  of  pure  tin-foil ; 
concentrated  nitric  acid. 

In  a  small  dry  flask  of  400-500  ccm.  (about  four 
ounces)  capacity  put  a  bit  of  granulated  tin  or  of 
pure  tin-foil.  Pour  upon  it  enough  concentrated 
nitric  acid  to  cover  it  and  place  the  flask  under  a  hood. 
If  no  change  takes  place  at  first,  heat  gently. 

What  evidence  have  you  that  change  is  taking 
place  ? 

Is  there  anything  in  this  experiment  which  sug- 
gests Experiment  12? 

What  is  left  behind  after  the  action  is  finished  ? 

Compare  the  properties  of  the  product  with  those 
of  tin. 


OXYGEN.  15 

OXYGEN. 
EXPERIMENT  15a* 

Hard-glass   (arsenic-)   tube  ;  rubber  tubing  ;    mercuric  oxide  ;  test- 
tubes  ;  pneumatic  trough. 

1.  Fill  the  bulb  of  an  arsenic-tube  nearly  full  of  red 
oxide  of  mercury ;  fit  a  piece  of  rubber  tubing  of  the 
proper  size  over  the  open  end  of  the  tube,  connecting 
it  in  turn,  if  necessary,  with  an  additional  delivery- 
tube  of  glass.     Heat  the  bulb  and   collect   the  gas 
given   off  in   test-tubes    standing  over   water   in  the 
pneumatic  trough.     (See  Experiment  5.) 

Is  the  gas  air  ?  Is  it  identical  with  that  obtained 
in  Experiment  11,  12,  or  13?  How  do  you  know? 

2.  Plunge  a  splinter  of  wood  with  a  spark  on  it 
into  the  gas.     What  happens  ? 

What  have  you  done  in  this  experiment  that  you 
did  not  do  in  Experiment  3  ? 

EXPERIMENT  16. 

Small  glass  retort  f;  clamp  stand  ;  pneumatic  trough;  cylinders  or 
test-tubes  ;  potassium  chlorate. 

1.  Into  a  clean,  dry  retort  put  4  or  5  grams  of  po- 

*  It  was  by  means  of  this  experiment  that  oxygen  was  discovered 
by  Priestley  and  Scheele  in  1774.  The  discovery  was  one  of  the 
highest  importance  for  chemistry. 

f  Instead  of  a  retort,  an  arsenic-tube  may  be  used  in  this  experi- 
ment, as  in  the  last ;  under  such  circumstances,  however,  only  a  very 
small  quantity  of  chlorate  can  be  used,  the  amount  of  oxygen  ob- 
tained will  be  small,  and  the  behavior  of  the  salt  under  the  action  of 
heat  cannot  be  so  well  studied.  Test-tubes,  being  made  of  soft  glass, 
are  rarely  capable  of  standing  the  heat  required  for  the  decomposi- 
tion of  potassium  chlorate. 

If  care  has  been  used  in  the  heating,  the  retort  will  not  have  been 
injured.  The  residue  can  be  washed  out  with  warm  water ;  after 
which,  if  the  retort  be  dried,  it  may  be  used  again  in  Experiment  18. 


16 


OXYGEN. 


EXPERIMENT  16— Continued. 

tassium  chlorate.     Connect  the  retort  with  a  delivery- 
tube  the  farther  end  of  which  dips  below  the  water  in 

the  trough.  Now  heat  the  re- 
tort gently  with  a  burner  and 
note  the  changes  which  take 
place.  Does  the  salt  melt? 
What  is  the  appearance  of 
boiling  due  to? 

2.  After  the  gas  has  driven 
most  of  the  air  out  of  the 
apparatus,  collect  what 
comes  off  in  cylinders. 
Meantime  what  changes  take 
place  in  the  chlorate  ?  Does 
it  remain  liquid?  If  not, 
does  it  melt  again  on  in- 
creasing the  heat?  Does  the  gas  continue  to  come 
off  after  the  second  melting  ? 

3.  After  further  heating  has  failed  to  drive  off  any 
more  gas,  withdraw  the  delivery-tube  from  the  trough 
that  air  may  enter  the  retort  as  it  cools.     What  is  the 
substance  left  in  the  retort  ? 

4.  Now  examine  the  gas  as  in  the  last  Experiment. 
Is  it  the  same  ? 

EXPERIMENT  17. 

Arsenic-tube  ;  pneumatic  trough  ;  test-tubes  or  cylinders  ;  manga- 
nese dioxide. 

Use  the  same  apparatus  as  in  Experiment  150,  but 
substitute  manganese  dioxide  for  mercuric  oxide. 
Heat  the  bulb  of  the  arsenic-tube  strongly.  Collect 
the  gas  as  before  ;  if  you  do  not  obtain  enough  by  a 


FIG.  6. 


OXYGEN.  17 

EXPERIMENT  17—  Continued. 

single  heating,  let  the  tube  cool,   empty  it,  refill  it 
with  fresh  dioxide,  and  heat  again. 

Unlike  potassium  chlorate  and  mercuric  oxide, 
manganese  dioxide  gives  up  but  a  portion  of  the  oxy- 
gen which  it  contains,  under  the  influence  of  heat. 

EXPERIMENT  18. 

Glass  retort,  etc.,  as  in  Experiment  16  * ;  potassium  chlorate ;  man- 
ganese dioxide. 

Mix  thoroughly  25-30  grams  (about  an  ounce)  of 
potassium  chlorate  with  an  equal  weight  of  granulated 
manganese  dioxide.f  Heat  the  mixture  carefully  in  a 
glass  retort  arranged  as  in  Fig.  6,  and  collect  the  gas  in 
a  number  of  cylinders,  bottles,  etc.  If  there  is  one 
available,  collect  the  gas  in  a  gasometer,  from  which 
it  can  be  drawn  oft'  as  it  may  be  needed. 

EXPERIMENT  19. 

Cylinder  or  bottle  containing  oxygen. 

Inhale  a  little  oxygen  from  one  of  the  bottles.  Can 
you  notice  any  odor  or  taste  ?  Oxygen  which  has 
been  prepared  by  the  method  described  in  Experi- 

*  Although  the  results  will  hardly  be  as  satisfactory,  yet,  if  neces- 
sary, smaller  vessels  may  be  used  for  collecting  the  gas,  and  5  to  10 
grams  of  potassium  chlorate  and  an  equal  weight  of  manganese  diox- 
ide employed  instead  of  the  quantities  given  above.  Instead  of  a 
retort,  a  good-sized,  stout  test-tube  fitted  with  a  cork  and  delivery- 
tube  may  be  used. 

f  Black  oxide  of  manganese  is  sometimes  adulterated  with  other 
substances,  and  when  heated  with  potassium  chlorate  it  may  then 
give  rise  to  explosions.  It  should  be  tested  before  using  by  mixing 
about  half  a  gram  of  it  with  an  equal  weight  of  potassium  chlorate 
and  heating  in  a  dry  test-tube.  If  the  decomposition  takes  place 
quietly  the  substance  may  be  used  for  the  preparation  of  oxygen. 


18  OXYGEN. 

EXPERIMENT  19—  Continued. 

ment  18  sometimes  Las  a  sharp  odor  due  to  the  pres- 
ence of  impurities.  This  is  especially  to  be  noticed  if 
the  heating  has  been  too  rapid.  On  standing  in  con- 
tact with  water  the  gas  gradually  becomes  freed  from 
these  impurities,  and  therefore  becomes  odorless. 

EXPERIMENT  20. 

Vessels  filled  with  oxygen  ;  deflagrating-spoons  ;  sulphur  ;  charcoal ; 
bit  of  phosphorus. 

1.  Turn  three  of  the  bottles  containing  oxygen  with 
the  mouth  upward,  leaving  them  covered  with  glass 
plates.     Into  one  introduce  a  little  sulphur  in  a  so- 
called  deflagrating-spoon,  which  is  a  small  cup  of  iron 
or  brass  attached  to  a  stout  wire  which  passes  through 
a  round  metal  plate,*  usually  of  tin  (see  Fig.  7).     In 
another  spoon  put  a  little  charcoal  (carbon),  and  in  a 
third  a  piece  of  phosphorus  f  about  the  size  of  a  pea. 
Introduce  each  into  a  jar  of  oxygen ;  let  them  stand 
quietly  and  notice  what  changes,  if  any,  take  place. 

2.  Does  oxygen  at  ordinary  temperature  act  readily 
upon  the  substances  used  in  the  experiments?     Does 
it  appear  to  act  at  all  on  the  sulphur  or  on  the  char- 
coal ?     What  evidence  of  action  have  you  in  the  case 
of  the  phosphorus  ? 

*  Such  plates  can  be  had  of  the  dealers.  One  that  will  answer  the 
purpose  can  be  made  by  punching  a  small  hole  through  the  centre 
of  the  cover  of  a  blacking-box.  Force  the  handle  of  the  spoon 
through  the  hole  so  that  it  is  held  firmly  in  place. 

f  Phosphorus  should  be  handled  with  great  care.  It  is  always 
kept  under  water,  usually  in  the  form  of  sticks.  When  a  small 
piece  is  wanted,  take  out  a  stick  with  a  pair  of  forceps,  and  put  it 
under  water  in  an  evaporating-dish.  While  it  is  under  the  water  cut 
off  a  piece  the  size  wanted.  Take  this  out  by  means  of  a  pair  of 


OXYGEN.  19 

EXPERIMENT  21. 

Same  apparatus  as  for  Experiment  20. 

1.  Under  a  hood  set  fire  to  a  little  sulphur*  in  a 
deflagrating-spoon  and  let  it  burn 

in  the  air.  Notice  whether  it 
burns  with  ease  or  with  diffi- 
culty. Notice  the  odor  of  the 
fumes  which  are  given  off. 

2.  Now  set  fire  to  another  small 
portion  and  introduce  it  in  the 
spoon   into    one   of  the   vessels 
containing  oxygen,  as  shown  in 
Fig.  7. 

Does  the  sulphur  burn  more  readily  in  the  oxygen 
or  in  the  air  ? 

3.  Notice  the  odor  of  the  fumes  given  off. 

Does  it  appear  to  be  the  same  as  that  given  off  when 
the  biirning  takes  place  in  the  air  ? 

EXPERIMENT  22. 

Same  apparatus  as  for  Experiment  20. 

Perform  similar  experiments  with  charcoal. 

What  takes  place  ? 

Explain  all  that  you  have  seen. 

EXPERIMENT  23.  f 

Same  apparatus  as  for  Experiment  20. 

Under  a  hood  burn  a  small  piece  of  phosphorus  in 
the  air  and,  again,  in  oxygen.     In  the  latter  case  the 

forceps,  lay  it  for  a  moment  on  a  piece  of  filter-paper,  which  will 
absorb  most  of  the  water,  then  quickly  put  it  in  the  spoon. 

*  Half  fill  the  spoon. 

f  It  may  be  as  well  for  the  teacher  to  perform  this  experiment. 


20  OXYGEN. 

EXPERIMENT  23—  Continued. 

light  emitted  from  the  burning  phosphorus  is  so  in- 
tense that  it  is  painful  to  some  eyes  to  look  at  it. 
After  the  burning  is  over  let  the  vessel  stand.  What 
has  been  formed  by  the  action  ? 

Does  the  vessel  become  clear? 

What  has  taken  place  ? 

EXPERIMENT  24. 

Vessel  of  oxygen  ;  old  watch-spring  (see  toot-note). 

Straighten  a  steel  watch-spring*  and  fasten  it  in  a 
piece  of  metal,  such  as  is  used  for  fixing  a  deflagratiug- 
spoon  in  an  upright  position ;  wind  a  little  wet  thread 
around  the  lower  end,  and  dip  it  in  melted  sulphur. 
Set  fire  to  the  sulphur,  and  insert  the  spring  into  a 
vessel  containing  oxygen. 

Describe  all  that  takes  place.  As  fast  as  the  spring 
is  consumed,  push  it  down  into  the  vessel. 

When  iron  is  exposed  to  the  air  what  is  the  color 
of  the  substance  formed  on  its  surface  ? 

Does  this  substance  suggest  anything  formed  in  the 
experiment  ? 

How  do  you  explain  the  resemblance  ? 

It  is  simple  enough,  but  phosphorus  is  a  dangerous  substance,  and 
the  burns  caused  by  it  heal  with  difficulty.  The  piece  of  phosphorus 
burned  should  be  about  the  size  of  a  small  pea.  It  should  be  put 
in  a  deflagrating-spoon,  and  this  should  be  held  in  the  middle  of  a 
rather  large  glass  vessel  containing  oxygen. 

*  Old  watch-springs  can  generally  be  had  of  any  watch-maker  or 
mender  for  the  asking.  A  spring  can  be  straightened  by  unrolling 
it,  attaching  a  weight,  and  suspending  the  weight  by  the  spring, 
The  spring  is  then  heated  up  and  down  to  redness  with  the  flame  of 
a  laboratory  burner  or  spirit-lamp. 


OXYGEN.  21 

EXPERIMENT  25. 

Apparatus  shown  in  Fig.  8  ;  fine  iron-filings. 

Arrange  an  apparatus  as  shown  in  Fig.  8.  A  is  a 
glass  tube  about  60  cm.  (2  feet)  long  and  3f  cm.  (1 J 
inches)  in  diameter.  This  is  connected  by  means  of 
a  bent  tube  with  the  small  flask  B,  of  50-100  cc. 


FIG.  8. 

capacity,  which  is  fitted  with  a  stopper  having  two 
holes.  This  flask  is  carefully  dried,  and  then  a  thin 
layer  of  iron-dust  or  fine  iron-filings  is  put  on  the 
bottom.  The  lower  end  of  A  dips  to  the  extent  of 
about  5  cm.  (2  inches)  in  water.  A  current  of  oxygen 


22      BURNING  IN  THE  AIR;  SLOW  COMBUSTION. 

EXPERIMENT  25— Continued. 

is  now  passed  through  the  apparatus  by  connecting 
at  C  with  a  generator  or  gasometer.  When  the  air 
has  thus  been  displaced  the  current  of  oxygen  is 
stopped,  and  the  stop-cock  at  the  end  of  G  is  closed. 
Now  heat  the  iron  gently  by  applying  a  flame  to  the 
flask.  When  the  iron  begins  to  glow,  remove  the 
flame. 

What  evidence  is  furnished  that  the  oxygen  enters 
into  combination  and  disappears  as  a  gas  ? 

What  change  has  the  iron  undergone  ? 


BURNING  IN  THE  AIE ;    SLOW   COMBUSTION. 
EXPERIMENT  25#. 

Small  porcelain  crucible ;  tripod ;  triangle ;   bit  of  lead ;  thick  iron 

wire. 

1.  In  a  small  porcelain  crucible  arranged  as  shown 
in  Fig.  9  put  a  bit  of  lead  the  size  of  a  ten-cent  piece. 
Heat  by  means  of  a  laboratory  burner, 
and   notice   the    changes   which   take 
place.     After  the  lead  has  melted  stir 
with  a  thick  iron  wire  while  heating. 
Continue   to  heat   and   stir  until  the 
substance  is  no  longer  liquid. 
What  is  its  appearance  now  ? 
2.  Let  it  cool. 
Is  it  lead  ? 

What  difference  is  there  between  the  action  in  this 
case  and  in  the  case  of  melting  ice  and  cooling  the 
water  down  again  ? 


DECOMPOSITION  OF  WATER;  HYDROGEN.       23 
EXPERIMENT  25£. 

Same  as  for  Experiment  25a,  together  with  some  borax. 

Repeat  Experiment  25a,  adding  enough  borax  to 
form  a  complete  cover  to  the  metal  after  the  borax 
and  the  metal  are  melted.  Do  not  stir  the  substances. 

Does  the  metal  melt  ? 

Is  it  changed  to  a  powder  f 

How  do  you  explain  the  difference  ? 

DECOMPOSITION   OF  WATEK ;    HYDROGEN. 
EXPERIMENT  26. 

Same  apparatus  as  in  Experiment  4. 

Eepeat  Experiment  4  and  examine  the  gases. 
"Which  is  the  hydrogen  ? 

EXPERIMENT  27. 

Sodium  ;  vessel  with  water. 

1.  Throw   a    small   piece    of    sodium  *    on    water. 
While  it  is  floating  on  the  surface  apply  a   lighted 
match  to  it. 

What  takes  place  ? 
What  causes  the  flame  ? 
Why  is  the  flame  yellow  ? 

2.  Place  a  small  piece  of  sodium  on  a  scrap  of  filter- 
paper  and  then  place  the  whole  on  the  water  of  the 
bath. 

What  difference  is  there  in  the  behavior  of  the 
sodium  from  that  first  noticed  ? 

*  The  metals  sodium  and  potassium  are  kept  under  kerosene  oil. 
When  a  small  piece  is  wanted,  take  out  one  of  the  larger  pieces 
from  the  bottle  and  cut  off  a  piece  the  size  needed.  It  is  not  advis- 
able to  use  a  piece  larger  than  a  small  pea.  Remove  the  oil  by  means 
of  filter-paper  before  throwing  it  on  the  water. 


24         DECOMPOSITION  OF  WATER;  HYDROGEN. 

EXPERIMENT  27—  Continued. 
What  reason  can  you  give  for  this  difference  ? 

3.  To  collect  a  little  of  the  gas  produced  by  the 
action  of  sodium  on  water,  fill  a  test-tube  with  water 
and  invert  it  in  the  trough.     Cut  off  a  piece  of  sodium 
not  larger  than  about  one-fourth  the  size  of  a  pea, 
wrap  it  in  filter-paper  after  having  removed  the  oil 
from  the  surface,  and  then  with  the  fingers  or  with  a 
pair  of  pincers  insert  it  in  the  test-tube,  the  mouth  of 
which  remains  all  the  while  under  water.     The  hy- 
drogen formed  will  rise  in  the  tube.     If  one  piece  of 
sodium  fails  to  fill  the  tube  use  a  second,  etc.     Do  not 
attempt  to  get  through  quickly  by  using  larger  pieces  of 
sodium. 

4.  When  the  tube  is  full  of  hydrogen  light  it,  as  in 
Experiment  4.     How  does  it  differ  from  air  ?     (Com- 
pare Experiment  13.) 

5.  Examine  the  water  on  which   the   sodium  has 
acted.     Do  you  notice  any  change  in  it  ?     Test  it  with 
pink  litmus-paper ;  what  action  has  it  ?    Test  hydrant- 
water  in  the  same  way ;  is  there  any  similar  action  on 
the  litmus-paper? 

What  has  become  of  the  sodium  ? 

EXPERIMENT  28. 

Porcelain  or  hard-glass   tube  ;   furnace  ;   iron-turnings ;   steam-gen- 
erating flask  ;  cylinders  ;  pneumatic  trough. 

Arrange  an  apparatus  as  in  Fig.  10.  By  means  of 
the  furnace  a  porcelain  or  hard-glass  tube,  nearly 
filled  with  iron-turnings,  is  heated  to  redness; 
through  this  tube  a  current  of  steam  generated  in  an 
appropriate  vessel  is  passed.  The  gas  which  is  set 
free  is  collected  in  cylinders  over  water. 


HYDROGEN  BY  ACTION  OF  ACIDS  ON  METALS.      25 

EXPERIMENT  28— Continued. 

Test  the  gas;  is  it  hydrogen?     What  has  become 
of  the  oxygen  ?     After  the  action  is  over,  open  the 


FIG.  10. 


tube  and  shake  out  the  iron-turnings.     What  change 
have  they  undergone  ? 

What  difference  is  there  in  the  action  of  iron  and  of 
sodium  on  water  ? 


HYDROGEN    BY    THE    ACTION    OF    ACIDS    ON 
METALS. 

EXPERIMENT  29.* 

Wolff's  flask  (Fig.  11)  or  wide-moutlied  bottle  (Fig.  12) ;  cylinders  or 
test-tubes  ;  granulated  zinc  ;  ordinary  hydrochloric  acid  ;  dilute 
sulphuric  acid. 

*  Always  be  cautious  when  working  with  hydrogen.  The  danger 
lies  in  the  fact  that  a  mixture  of  hydrogen  and  oxygen  or  of  hydro- 
gen and  air  explodes  violently  when  a  spark  or  flame  comes  in  contact 
with  it.  When  collecting  it  in  quantity,  always  let  the  gas  escape  for 
a  time,  from  3  to  5  minutes  or  longer  if  the  acid  acts  slowly  upon  the 
zinc,  and  then,  before  applying  a  flame  to  it,  collect  a  test-tube  full 
and  light  it  to  see  whether  it  will  burn  quietly  without  explosion. 
If  it  will  not,  wait  longer. 


26     HYDROGEN  BY  ACTION  OF  ACIDS  ON  METALS. 

EXPERIMENT  29—  Continued. 

1.  In  a  cylinder  or  test-tube  put  a  few  pieces  of 
granulated  zinc,  and  pour  upon  it  enough  ordinary 
hydrochloric  acid  to  cover  it. 

What  do  you  notice  ? 

2.  After  the  action  has  continued  for  a  minute  or 
two,  apply  a  lighted  match  to  the  mouth  of  the  vessel. 

What  takes  place  ? 

3.  Try  the  same  experiments  using  sulphuric  acid 


FIG.  11.  FIG.  12. 

which  has  been  diluted  with  four  times  its  volume  of 
water.  * 

What  is  the  result  ? 

What  is  the  gas  given  off? 

For  the  purpose  of  collecting  hydrogen  the  gas 
should  be  evolved  from  a  bottle  with  two  necks  called 

*  To  dilute  ordinary  concentrated  sulphuric  acid  with  water,  the 
acid  should  be  poured  slowly  into  the  water  while  the  mixture  is  con- 
stantly stirred.  If  the  water  is  poured  into  the  acid,  the  heat  evolved 
at  the  places  where  the  two  liquids  corue  in  contact  with  each  other 
may  be  so  great  as  to  convert  the  water  into  steam  and  cause  the 
strong  acid  to  spatter. 


THE  ACTION  OF  ACIDS  ON  METALS.  27 

EXPERIMENT  29— Continued. 

a  "Wolff's  flask  (see  Fig.  11),  or  a  wide-mouthed  bottle 
in  which  is  fitted  a  cork  with  two  holes  (see  Fig.  12).  * 
Put  a  small  handful  of  granulated  zinc  f  into  the 
bottle  and  pour  upon  it  enough  cooled  dilute  sulphuric 
acid  (1  volume  concentrated  acid  to  4  volumes  of 
water)  to  cover  it.  The  acid  is  introduced  through 
the  funnel-tube,  which  reaches  nearly  to  the  bottom 
of  the  flask.  Allow  the  action  to  proceed  several 
minutes  before  collecting  any  of  the  gas ;  this  is  to 
allow  the  hydrogen  time  to  displace  all  the  air  in  the 
generator.  Collect  by  displacement  of  water,  as  in 
the  case  of  oxygen.  Should  the  action  become  slow 
add  a  little  more  of  the  dilute  acid.  Fill  four  or  five 
cylinders  and  bottles  with  the  gas. 

THE  ACTION  OF  ACIDS  ON  METALS. 
EXPERIMENT  30. 

Same  apparatus  as  in  Experiment  29. 

After  the  action  of  the  acid  on  the  zinc  (see  last  Ex- 
periment) is  over,  pour  the  contents  of  the  generator 
into  a  filter  and  collect  the  filtrate  in  a  beaker.  Evap- 
orate this  solution  until  it  begins  to  crystallize  and 

*  In  working  with  hydrogen,  indeed  with  all  gases,  the  greatest 
care  should  be  used  to  make  all  joints  tight.  Roll  all  corks  well  be- 
fore using  them,  and  bore  them  so  that  the  delivery-tubes  fit  snugly 
into  place. 

f  Some  zinc,  particularly  that  which  is  pure,  does  not  act  readily 
upon  acids.  Whether  the  action  is  taking  place  freely  or  not  can  be 
seen  by  the  effervescence  in  the  flask  and  by  the  rate  at  which  bub- 
bles of  gas  appear  at  the  end  of  the  delivery-tube  when  this  is  placed 
under  water.  If  the  action  is  slow,  wait  longer  before  collecting  it 
and  before  setting  fire  to  it.  It  is  better  not  to  use  zinc  which  acts 
slowly. 


28  PURIFICATION  OF  HYDROGEN. 

EXPERIMENT  30—  Continued. 

then  let  it  cool.     Sulphate  of  zinc  will  crystallize  out. 
Dry  the  crystals  and  preserve  them  for  future  use. 

PURIFICATION  OF  HYDROGEN. 
EXPERIMENT  31. 

Hydrogen-generator;  wash-cylinder  or  U-tube;    potassium  perman- 
ganate. 

Pure  hydrogen  is  odorless;  hydrogen  prepared 
from  impure  zinc  is  mixed  with  other  gases  which 
possess  odors.  To  remove  the  latter  the  gas  should 
be  "  washed  "  with  a  solution  of  potassium  perman- 


FIG.   13. 


gaiiate,  a  substance  which  destroys  the  impurities  but 
has  no  effect  on  the  hydrogen.  Fig.  13  shows  the 
necessary  apparatus.  The  hydrogen-generator  is  con- 
nected with  a  cylinder  A  containing  a  dilute  solution 
of  potassium  permanganate  so  that  the  gas  bubbles 
up  through  the  solution.  As  it  is  frequently  difficult  to 


HYDROGEN.  29 

EXPERIMENT  31— Continued. 

obtain  corks  of  sufficient  size  and  at  the  same  time  tight 
enough  for- such  a  wash-cylinder,  it  is  often  better  to 
use  a  "  U-tube  "  of  about  J-inch  bore.  The  solution 
just  closes  the  bend  of  the  tube,  forming  a  "  trap." 
The  gas  from  the  generator  enters  one  limb  of  the 
U-tube,  pushes  past  the  liquid  and  enters  the  delivery- 
tube  from  the  other  limb.  With  corks  of  the  small 
size  thus  called  for  it  is  easy  to  make  joints  perfectly 
tight. 

HYDKOGEN. 
EXPERIMENT  32.* 

Cylinder  filled  with  hydrogen. 

Place  a  vessel  containing  hydrogen  with  the  mouth 
upward  and  uncovered.  In  a  short  time  examine  the 
gas  and  see  whether  it  is  hydrogen. 

EXPERIMENT  33. 

Two  cylinders,  one  filled  with  hydrogen. 

Bring  the  mouth  of  a  vessel  containing  hydrogen 
below  an  inverted  vessel  con- 
taining air,  and  then  grad- 
ually lower  it,  keeping  the 
mouths  of  the  two  cylinders 
together,  in  the  way  shown 
in  Fig.  14.  By  this  means 
the  hydrogen  is  poured  up  FlG.  14. 

from  the  lower  vessel  into  the  upper. 

*  In  all  experiments  with  hydrogen  see  that  no  flames  are  burning 
near  you. 


30  HYDROGEN. 

EXPERIMENT  33—  Continued. 

Is  there  hydrogen  in  the  vessel  with  the  mouth  up- 
ward? 

Is  there  hydrogen  in  the  other  vessel  ? 

EXPERIMENT  34. 

Soap-suds;  clay  pipe;  hydrogen  generating-flask. 

Soap-bubbles  filled  with  hydrogen  rise  in  the  air. 
The  experiment  is  best  performed  by  connecting  an 
ordinary  clay  pipe  by  means  of  a  piece  of  rubber  tub- 
ing with  the  exit-tube  of  a  flask  in  which  hydrogen  is 
being  generated.  This  experiment  can  be  conveniently 
performed  by  hanging  up,  about  six  to  eight  feet  above 
the  experiment-table,  a  good-sized  tin  funnel-shaped 
vessel  with  the  mouth  downward.  Now  place  a  gas- 
jet  or  a  small  flame  of  any  kind  at  the  mouth  of  the 
vessel.  If  the  soap-bubbles  are  allowed  to  rise  below 
this  apparatus  they  will  come  in  contact  with  the  flame 
and  explode  at  once. 

Small  balloons  of  collodion  are  also  made  for  show- 
ing the  lightness  of  hydrogen.  Large  balloons  are 
always  filled  with  hydrogen  or  some  other  light  gas. 
Some  kinds  of  illuminating-gas  are  rich 

Lin  hydrogen,  and  may  therefore  be  used 
for  the  purpose. 
EXPERIMENT  35. 
Platinum  tube,  or  glass  tube  and  platinum-foil; 
hydrogen-generator. 
If  there   is   no   small    platinum    tube 
available,  roll  up  a  small  piece  of  plati- 
num-foil  and  melt  it  into  the  end  of  a 
glass  tube,  as  shown  in  Fig.  15.     Often 
the  tip  of  a  blowpipe  can  be  used  with  practically  as 


WATER. 


31 


EXPEEIMENT  35 — Continued. 

good  results.  Connect  this  burner  with  a  source  of 
hydrogen*  and,  after  allowing  the  hydrogen  time  to 
displace  all  air  from  the  apparatus,  light  it.  It  will 
be  seen  that  the  flame  is  almost  colorless  and  gives  no 
light.  Is  it  very  hot  ?  Try  it  with  a  platinum  wire,  etc. 

EXPERIMENT  36. 

Taper  fastened  on  wire;  cylinder  full  of  hydrogen. 

1.  Hold  a  wide-mouthed  bottle 
or  cylinder   filled  with    hydrogen 
with    the    mouth  downward.     In- 
sert into  the  vessel  a  lighted  taper 
held  on  a  bent  wire,  as  shown  in 
Fig.  16. 

What  do  you  observe  ? 

What  burns  ? 

Does  the  taper  continue  to  burn  ? 

2.  Withdraw  the  taper  and  hold 
the  wick  for  a  moment  in  the  flame 
at  the  mouth  of  the  cylinder,  then 

withdraw  it  entirely.  Put  it  back  again  in  the  hydrogen. 
Does  hydrogen  support  combustion  ? 
Does  it  burn  ? 

3.  Try  similar  experiments  using  a  splinter  of  wood 
in  place  of  the  taper. 

WATER. 
J  .  .  EXPERIMENT  37. 

Dry  test-tube  ;  bit  of  wood ;  bit  of  fresh  meat. 
1.  In  a  dry  test-tube  heat  gently  a  small  piece  of  wood. 
What  evidence  do  you  obtain  that  water  is  given  off? 

*  The  hydrogen  must  not  bubl)le  through  any  liquid  on  its  way  to 
the  burner,  otherwise  it  will  come  in  puffs  and  will  not  burn  steadily. 


FIG.  16. 


32  WATER  OF  CRYSTALLIZATION. 

EXPERIMENT  37— Continued. 
2.  Do  the  same  thing  with  a  piece  of  fresh  meat. 
Is  water  driven  off  in  this  case  ? 

CRYSTALS  AND  WATER  OF  CRYSTALLIZATION. 

Most  substances  which  dissolve  in  water  are  more 
soluble  in  hot  water  than  in  cold.  In  a  hot  solution 
there  may  therefore  be  more  of  a  substance  than  can 
remain  in  solution  when  cool.  On  cooling  the  sub- 
stance will  in  many  cases  be  deposited  in  masses  of 
regular  shape,  which  are  called  crystals. 

These  crystals  in  some  cases  contain  water  held  in  a 
kind  of  combination  ;  the  crystals  may  be  perfectly  dry 
and  yet  when  heated  may  readily  give  off  water- vapor. 
Indeed  in  some  cases  the  water  passes  off  at  ordi- 
nary temperatures,  especially  if  the  crystals  be  placed 
in  dry  air.  Examples  of  crystals  containing  "  water 
of  crystallization"  are  :  zinc  sulphate,  gypsum,  copper 
sulphate,  sodium  sulphate. 

WATER  OF   CRYSTALLIZATION. 
EXPERIMENT  38. 

Zinc  sulphate  crystals  ;  test-tube. 

Take  some  of  the  crystals  of  zinc  sulphate  ("  white 
vitriol  ")  obtained  in  Experiment  30  and  examine  them 
to  see  if  they  are  quite  dry.  If  they  are  moist  remove 
the  moisture  by  pressing  them  between  layers  of  filter- 
paper.  Note  their  shape  and  appearance.  Now  heat 
them  gently  in  a  dry  tube. 

What  evidence  have  you  that  they  contained  water? 
What  changes  do  the  crystals  suffer  ?  Is  the  crystal- 
line form  dependent  upon  the  presence  of  water  of 
crystallization  ? 


EFFLORESCENT  COMPOUNDS.  33 

EXPERIMENT  39. 

Piece  of  gypsum  ;  dry  test-tube. 

In  a  dry  test-tube  heat  gently  a  piece  of  gypsum  the 
size  of  a  small  marble.  Gypsum  is  the  natural  sub- 
stance from  which  "  plaster  of  Paris"  is  made. 

What  evidence  have  you  that  water  is  contained  in 
this  substance  ? 

What  is  the  substance  which  is  left  behind  after  the 
heating  ?  What  is  its  appearance  ? 

EXPERIMENT  40. 

Few  small  crystals  of  copper  sulphate ;  porcelain  evaporating-dish. 

1.  In  a  porcelain  evaporating-dish  heat  gently  a  few 
small  crystals  of  copper  sulphate  ("  blue  vitriol  "). 

What  change  besides  the  escape  of  water  do  you 
notice  ? 

What  is  the  color  of  the  powder  which  is  left  be- 
hind ? 

2.  Dissolve  this  powder  in  a  little  hot  water. 
What  is  the  color  of  the  solution  ? 

3.  Evaporate  off  some  of  the  water  and  let  the  solu- 
tion cool.     Kepeat  this,  if  necessary,  until  on  cooling 
crystals  are  deposited. 

What  is  the  color  of  the  crystals  ? 
Do  these  crystals  in  any  way  suggest  those  with 
which  you  started  ? 

Where  did  the  salt  get  its  "  water  of  crystallization  "  ? 

EFFLOKESCENT  COMPOUNDS. 
EXPERIMENT  41. 

Crystals  of  sodium  sulphate  ;  watch-glass. 
Select  a  few  crystals  of  sodium  sulphate,  or  Glau- 
ber's salt,  which  have  not  lost  their  lustre.     Put  them 


34  HYDROGEN  AND  OXYGEN  IN  WATER. 

EXPERIMENT  41 — Continued. 

on  a  watch-glass,  and  let  them  lie  exposed  to  the  air 
for  an  hour  or  two. 

What  evidence  have  you  that  change  takes  place  ? 

Compare  their  behavior  with  that  of  the  crystals  of 
zinc  sulphate. 

What  does  this  experiment  show  with  regard  to  the 
nature  of  the  air  ? 

DELIQUESCENT   COMPOUNDS. 
EXPERIMENT  42. 

Calcium  chloride  ;  watch-glass. 

Expose  a  few  pieces  (the  size  of  a  pea)  of  dry  cal- 
cium chloride  to  the  air.  Calcium  chloride  was  the 
product  obtained  in  Experiment  11.  If  there  is  none 
in  the  laboratory,  make  some. 

What  change  takes  place  when  the  substance  is  ex- 
posed for  some  time  to  the  air  ? 

Compare  the  action  in  this  case  with  that  in  the  case 
of  zinc  sulphate  ;  of  sodium  sulphate. 

What  does  this  experiment  show  with  regard  to  the 
constituents  of  the  air? 

HYDROGEN   AND   OXYGEN  IN  WATER. 
EXPERIMENT  43. 

Same  apparatus  as  in  Experiment  4. 

Repeat  Experiment  4,  using  graduated  tubes  to  col- 
lect the  gases  ;  tubes  divided  to  indicate  cubic  centi- 
meters are  the  most  convenient.  It  will  be  seen  that 
just  twice  as  many  cc.  of  one  gas  are  obtained  as  of 
the  other.  On  examining  the  gases,  the  larger  volume 
will  be  found  to  be  hydrogen  and  the  smaller  volume 
oxygen. 


WATER  BY  BURNING  HYDROGEN  IN  AIR.        35 

EXPERIMENT  43— Continued. 

As  the  action  takes  place  if  pure  water  and  pure 
sulphuric  acid  are  used,  and  as  the  same  amount  of 
sulphuric  acid  is  found  to  be  still  present  no  matter 
how  long  the  action  is  continued,  it  is  evident  that  the 
gases  have  been  produced  by  the  decomposition  of 
the  water. 

Since,  too,  nothing  new  is  produced  except  the  two 
gases,  and  since  also  the  sum  of  their  weights  is  equal 
to  the  weight  of  the  water  decomposed,  it  follows  that 
water  is  composed  of  hydrogen  and  oxygen  combined 
in  the  proportion  of  two  to  one  by  volume. 

WATER  PEODUCED  BY   THE   BURNING   OF 
HYDROGEN  IN  THE  AIR. 

EXPERIMENT  44. 

Hydrogen-generator ;  U-tube  ;  calcium  chloride  ;  bell- jar  or  bottle. 


FIG.  17. 

In  order   to  show  that   water  is  produced  by  the 


36  ELECTROLYTIC  GAS. 

EXPEEIMENT  44— Continued. 

-burning  of  hydrogen  we  should  have  the  gas  dry. 
For  this  purpose  it  is  passed  through  a  tube  contain- 
ing calcium  chloride,  since  this  substance  has  the 
power  of  absorbing  moisture. 

1.  Connect  a  hydrogen-generator  with  one  limb  of  a 
U-tube   filled  with  lumps  of  calcium    chloride  ;    the 
other  limb  is  connected  with  a  tip  for  burning  the  gas 
(see  Fig.  17).     After  the  hydrogen  has  been  allowed 
to  run  to  displace  all  air  in  the  apparatus,  bring  a 
cold   glass   plate   into   the  jet  of  hydrogen.     Is   any 
moisture  deposited  ?     Why  ? 

2.  Now   withdraw    the    plate  and    light  the   gas.* 
Bring  a  cold  dry  bell-jar  or  bottle  over  the  hydrogen 
flame.     Is  moisture  deposited  ?     Where  was  it  formed  ? 

ELECTROLYTIC   GAS. 
EXPERIMENT  45.  f 

Gasometer  containing  a  small  quantity  of  a  mixture  of  hydrogen  and 
oxygen  ;  soap-suds  ;  pipe. 

1.  A  mixture  of  hydrogen  and  oxygen  in  the  propor- 
tion of  two  volumes  to  one  is  called  "  electrolytic  gas," 
because  it  is  formed  by  the  electrolysis  of  water. 
Make  a  small  quantity  of  such  a  mixture  in  a  gasom- 
eter, taking  great  care  to  keep  all  flames  out  of  the 
way.  Connect  the  gasometer  with  a  clay  pipe  by 
means  of  a  rubber  tube  and  allow  the  gas-mixture  to 
bubble  through  some  soap-suds  in  an  evaporating- 
dish.  Shut  off  the  gas  and,  by  means  of  a  taper  on 

*  The  gas  must  be  lit  before  the  bell-jar  is  placed  over  the  jet ; 
otherwise  the  hydrogen  will  be  mixed  with  the  air  in  the  bell-jar 
and  may  explode  on  bringing  a  flame  near  it. 

f  This  experiment  had  better  be  performed  by  the  teacher  only. 


ACTION  OF  HYDROGEN  ON  HOT  COPPER  OXIDE.    37 

EXPERIMENT  45— Continued. 

the  end  of  a  stick,  light  the  froth  on  the  soap-solution. 
What  happens  ? 

2.  Bubbles  of  electrolytic  gas  will  rise  in  air.  Blow 
some  with  the  pipe,  as  in  the  case  of  hydrogen  (Ex- 
periment 34). 


ACTION  OF  HYDKOGEN  ON  HOT  COPPER 
OXIDE. 

EXPERIMENT  46. 

Apparatus  shown  in  Fig.  18. 

Arrange  an  apparatus  as  shown  in  Fig.  18.     A  is  a 
Wolff's  liask  for   generating   hydrogen.     To   remove 


FIG.  18. 

impurities  the  gas  is  passed  through  a  solution  of  po- 
tassium permanganate  contained  in  the  wash-cylinder 
J3.*  The  cylinder  C  contains  concentrated  sulphuric 

*  Instead  of  the  wash-cylinders  B  and  G,  U-tubes  may  with  advan- 
tage be  used  as  described  in  Experiment  31. 


38  OXYHYDROGEN  BLOWPIPE. 

EXPERIMENT  46 — Continued. 

acid,  and  the  U-tube  D  contains  granulated  calcium 
chloride,  both  of  them  serving  to  remove  the  moisture 
with  which  the  hydrogen  is  saturated  after  bubbling 
through  B.  The  tube  E\$>  of  hard  glass  and  contains 
a  layer  of  black  copper  oxide  ;  the  bulb  at  E  is  of  ad- 
vantage, but  is  not  essential.  The  tube  should  either 
be  drawn  out  as  represented  in  the  figure,  or  else  be 
connected  by  means  of  a  cork  with  a  piece  of  glass 
tubing  of  small  bore.  The  object  of  this  is  to  con- 
dense the  vapor  formed  in  E.  After  the  apparatus  is 
filled  with  hydrogen  the  tube  containing  the  copper 
oxide  is  heated  with  a  burner  to  low  redness. 

What  evidence  do  you  have  of  the  formation  of 
water?  What  change  takes  place  in  the  copper 
oxide  ?  After  the  action  of  the  hydrogen  upon  the 
copper  oxide  has  ceased,  let  the  tube  cool  while  the 
hydrogen  still  passes  through  it.  Then  try  the  action 
of  a  little  dilute  nitric  acid  on  some  of  the  black 
copper  oxide  you  started  with  and  on  the  substance 
left  in  the  tube.  What  difference  do  you  note  ? 


OXYHYDROGEN  BLOWPIPE. 
EXPERIMENT  47. 

Oxyhydrogen  blowpipe  ;  iron  wire  ;  steel  spring,  etc. 

Hold  in  the  flame  of  the  oxy hydrogen  blowpipe 
successively  a  piece  of  iron  wire,  a  piece  of  steel  watch- 
spring,  a  piece  of  copper  wire,  a  piece  of  zinc,  a  piece 
of  platinum  wire. 

Describe  what  happens  in  each  case. 


DISTILLATION  OF  WATER. 


39 


EXPERIMENT  48. 

Blowpipe,  as  before  ;  piece  of  lime. 

Cut  a  piece  of  liine  of  convenient  size  and  shape, 
say  25  mm.  (1  inch)  long  by  20  mm.  (f  inch)  wide  and 
the  same  thickness.  Fix  it  in  position  so  that  the 
flame  of  the  oxyhydrogen  blowpipe  shall  play  upon 
it.  The  light  is  very  bright,  but  by  no  means  as  in- 
tense as  the  electric  light. 


DISTILLATION  OF  WATER. 
EXPERIMENT  49. 

Apparatus  shown  in  Fig.  19  ;  ammonia  solution  ;  copper  sulphate. 
Arrange  an  apparatus  as  shown  in  Fig.  19.     The 
water  to  be  distilled  is  placed  in  the  flask  A.    The 


FIG.  19. 

steam  formed  in  A  passes  through  B  into  the  con- 
denser-tube C.  This  tube  is  kept  cool  by  being  sur- 
rounded by  a  jacket  of  cold  water  DE;  a  continuous 
supply  of  fresh  water  enters  at  E,  and  the  warm  water 
at  F  flows  out  through  the  tube  H.  The  distilled 
water  is  caught  in  the  receiver  K* 


40  WATER  AS  A  SOLVENT. 

EXPERIMENT  49—  Continued. 

1.  See  that  your   condenser   is    clean.     Then   put 
about  500  cc.  of  water  in  A,  add  to  it  75-100  cc.  dilute 
ammonia  solution,  and  distil  into  a   clean   receiver. 
When  about  150  cc.  has  distilled  over,  stop  the  heat- 
ing, and  examine  the  distillate. 

Does  it  smell  of  ammonia  ?  Has  it  any  effect  on 
pink  litmus-paper  ?  Is  it  possible  by  distillation  to 
separate  from  water  a  volatile  constituent  like  am- 
monia ? 

2.  Kemove  the  stopper  from  the  distilling  flask  and 
add  enough  copper  sulphate  to  color  the  solution  a 
decided    blue.     After  it   has   dissolved,    replace   the 
stopper  and  distil  a  second  portion  into  a  clean  flask. 
Is  the  distillate   colored  ?     Is  it  possible  by  distilla- 
tion to  separate  from  water  a  non-volatile  constituent 
like  copper  sulphate  ? 

WATER  AS   A  SOLVENT. 
EXPERIMENT  49«. 

Two  flasks  (200-250  cc.)  with  stoppers  ;    common  salt ;    potassium 

chlorate. 

1.  Into  each  of  two  clean  dry  200-250  cc.  flasks 
provided  with  well-fitting  corks,  pour  just  100  cc. 
filtered  water  and  weigh  as  accurately  as  you  can. 
Label  the  flasks,  say,  "  I  "  and  "  II."  Now  add  com- 
mon salt,  a  few  grams  at  a  time,  to  one  of  them  until 
the  water  will  dissolve  no  more  on  thorough  shaking. 
Weigh  again  and  calculate  how  much  salt  has  been 
dissolved.  To  the  other  flask  add  potassium  chlorate, 
in  quantities  of  not  more  than  a  gram  at  a  time, 
and,  when  a  saturated  solution  is  obtained,  weigh. 


SOL  UTION  WITH  AND  WITHO  UT  CHEMICAL  CHANGE.   41 

EXPERIMENT  49&  —  Continued. 

Compare  the  relative  solubilities  of  the  two  sub- 
stances in  cold  water. 

2.  Now  heat  the  water  in  the  two  flasks  nearly  to 
boiling;  place  them  side  by  side  on  the  water-bath. 
Add  more  salt,  a  grain  only  at  a  time,  to  the  solution 
of  common  salt,  and  more  potassium  chlorate,  ten 
grams  at  a  time,  to  the  chlorate  solution.  When  the 
solutions  are  saturated,  weigh  again. 

Compare  the  relative  solubilities  of  the  two  sub- 
stances in  hot  water. 

Compare  the  relative  solubility  of  each  in  hot  and 
in  cold  water. 

Does  the  common  salt  crystallize  out  as  the  solution 
cools  ?  If  so,  to  what  extent  ?  How  does  the  chlorate 
solution  behave  on  cooling? 

SOLUTION  WITH  AND  WITHOUT   PERMANENT 
CHEMICAL   CHANGE. 


EXPERIMENT 

Beakers  ;  sodium  carbonate  ;  dilute  sulphuric  acid. 

1.  Dissolve  25  grams  of  crystallized  sodium  carbon- 
ate in  enough   hot  water  to  form  a  clear  solution. 
Divide  in  two  portions  ;  set  one  aside  to  cool. 

Do  the  crystals  form  again  ?  Are  they  like  those 
with  which  you  started? 

Dissolve  a  little  of  each  in  water  :  is  the  solution 
acid  or  alkaline  to  litmus-paper?  Treat  each  with  a 
little  dilute  hydrochloric  acid  :  do  they  behave  alike  ? 
Rub  a  little  of  each  solution  between  the  fingers  :  are 
they  alike  ? 

2.  To  the  second  portion  of  the  original  carbonate. 


42  SOLUTION  AIDS  CHEMICAL  ACTION. 

EXPERIMENT  49 J— Continued. 

solution  add,  a  few  drops  at  a  time,  dilute  sulphuric 
acid  until  the  solution  just  becomes  acid  to  litmus- 
paper  ;  evaporate  off  ^  to  ^  the  liquid  and  allow  it  to 
cool  and  crystallize. 

Compare  the  crystals  with  those  of  the  original  car- 
bonate. 

Are  they  the  same?  Is  the  solution  of  the  new 
crystals  alkaline ;  does  it  feel  soapy  between  the  fin- 
gers ;  has  hydrochloric  acid  any  effect  on  it  ? 

Explain  the  results  you  have  obtained. 

Has  solution  in  water  changed  the  carbonate  ?  Has 
solution  in  dilute  sulphuric  acid  ? 

SOLUTION  AIDS   CHEMICAL  ACTION. 
EXPERIMENT  49c. 

Dry  mortar  ;  test-tubes ;  dry  tartaric  acid ;  dry  sodium  bicarbonate. 

1.  Mix  together  in  a  dry  mortar  about  a  gram  of  dry 
tartaric  acid  and  about  an  equal  quantity  of  dry  sodium 
bicarbonate. 

Do  you  see  any  evidence  of  action  ? 

2.  Now  dissolve  about  a  gram  of  tartaric  acid  in  4-5 
cc.  of  water  in  a  test-tube,  and  about  the  same  quan- 
tity of  the  bicarbonate  in  water  in  another  test-tube. 
Pour  the  two  solutions  together. 

What  evidence  have  you  now  that  action  takes  place  ? 

3.  Pour  water  upon  the  dry  mixture  first  made. 
Does   action   take   place?     What  causes  the  bub- 
bling ? 

Will  a  match  burn  in  the  gas?  In  which  experi- 
ment already  performed  was  a  similar  gas  obtained  ? 


WEIGHT  OF  OXYGEN  IN  POTASSIUM  CHLORATE.   43 

EXPERIMENT  49of. 

Small  dry  mortar  ;  test-tubes  ;  dry  iron  sulphate  (green  vitriol) ;  dry 
potassium  ferrocyanide. 

1.  Mix  together  in  a  dry  mortar  about  a  gram  of  dry 
sulphate  of  irou  ("green  vitriol  ")  and  about  a  gram  of 
dry  ferrocyanide  of  potassium  ("yellow  prussiate  of 
potash"). 

Does  action  take  place  ? 

2.  Make  a  solution  of  each  of  the  two  substances 
and  pour  them  together  in  a  test-tube.* 

What  evidence  have  you  that  action  takes  place  ? 

3.  Pour  water  on  the  dry  mixture. 
Does  action  take  place  ? 

THE  WEIGHT  OF  OXYGEN  IN  A  GIVEN  WEIGHT 
OF  POTASSIUM  CHLORATE. 

EXPERIMENT  50. 

Hard-glass  tube  •  potassium  chlorate  ;  asbestos ;  gas-burettes  (100  cc. 
size  are  perhaps  best). 

Clean  and  dry  very  carefully  a  piece  of  hard-glass 
tubing  about  10  cm.  (4  inches)  long  and  8-10  mm. 
(about  £  inch)  internal  diameter,  closed  at  one  end, 
and  weigh  it  on  a  delicate  balance  as  accurately  as 
you  can.  Next  weigh  off  a  little  less  than  0.3  gram  of 
pure  dry  potassium  chlorate :  this  weighing  need  not 
be  very  accurate.  Transfer  the  chlorate  to  the  tube 
and  weigh  the  tube  carefully  again.  By  subtracting 
the  weight  of  the  empty  tube  from  this  we  obtain  the 
exact  weight  of  chlorate  used.  Now  heat  a  small 
bunch  of  asbestos  in  the  burner-flame  to  drive  off  any 

*  Use  about  the  same  quantities  of  the  substances  as  directed  in 
Experiment  49c. 


44    WEIGHT  OF  OXYGEN  IN  POTASSIUM  CHLORATE. 

EXPERIMENT  50— Continued. 

moisture  and  decompose  any  organic  matter  it  may 
contain,  and  then  push  it  gently  into  the  tube  and 
down  upon  the  chlorate.  -g 

The  asbestos  will  thus    f 
form  a  porous  plug  in 
the  tube  and  will  pre- 
vent spattering  of  the 
chlorate     when     it     is  FlG  20- 

heated.  Next  heat  the  tube  near  the  open  end  in  the 
flame  of  a  blast-lamp  and  draw  it  out  as  represented 
in  Fig.  20.  This  is  to  enable  you  to  attach  the  tube 
to  the  gas-burettes.  Now  weigh  the  tube  for  the  third 
time ;  after  this  you  are  ready  for  the  heating.  Con- 
nect the  tube  by  means  of  a  short  piece  of  black 
rubber  tubing  to  the  gas-burette  A  *  (Fig.  20),  tying 
the  joints  tight  with  thread.  The  tube  A  should  be 
filled  with  water  nearly  to  the  top  of  the  graduation 
before  the  chlorate-tube  is  attached ;  this  is  done  by 
simply  raising  the  reservoir-tube  B.  Now  read  the 
volume  of  air  in  the  burette  carefully.  Everything 
being  ready,  holding  the  chlorate-tube  out  from  the 
burette  by  means  of  a  test-tube  holder,  heat  the  lower 
end  very  gently  with  the  burnjer.  The  chlorate  first 
melts  and  then  begins  to  give  off  oxygen ;  the  water 
in  A  will  fall  and  that  in  B  will  rise.  Let  the  evolu- 
tion of  gas  be  very  slow  :  too  rapid  heating  drives 
some  of  the  solid  material  over  with  the  oxygen,  in 
spite  of  the  asbestos.  During  the  heating  it  is  best 
to  keep  the  level  of  the  water  in  the  tubes  A  and  B 
the  same,"  that  the  hot  tube  may  suffer  no  change  of 

*  The  glass  stop  cocks  on  A  are  not  necessary  for  this  experiment : 
a  plain  burette  will  serve  as  well. 


WEIGHT  OF  OXYGEN  IN  POTASSIUM  CHLORATE.   45 


EXPERIMENT  50 — Continued. 
volume.  When  no  more  gas  is 
apparently  given  off,  heat  the  end 
of  the  chlorate  tube  and  the  asbes- 
tos to  a  red  heat,  and  then  let  the 
apparatus  cool  for  fifteen  minutes. 
The  volume  of  the  gas  is  then 
carefully  read  again  and,  by  sub- 
tracting the  volume  read  before 
the  heating,  we  thus  obtain  the 
volume  of  oxygen  driven  off.  De- 
termine the  temperature  of  the 
room  near  your  apparatus  with 
the  aid  of  an  accurate  centigrade 
thermometer;  make  a  careful 
reading  of  the  barometer  ;  find  the 
tension  of  aqueous  vapor,  for  the 
temperature  noted,  and  you  have 
the  data  for  calculating  the  vol- 
ume the  oxygen  obtained  would 
occupy  under  standard  conditions. 
Lastly,  detach  the  chlorate-tube 
from  the  burette,  wipe  it  off  care- 
fully and  weigh  it :  the  loss  in 
weight  since  the  last  weighing 
represents  the  weight  of  the  oxy- 
gen driven  off. 

We  know  therefore  the  weight 
of  chlorate  used  and  the  weight 
of  oxygen  given  off  from  it ;  it  is 
now  easy  to  calculate  the  percent- 
age of  oxygen  in  the  chlorate. 
But  the  weight  of  the  oxygen  can 


Fia.  21. 


46    WEIGHT  OF  OXYGEN  IN  POTASSIUM  CHLORATE. 

EXPEKIMENT  50—  Continued. 

be  found  in  another  way  :  Let  v  represent  the  volume 
of  oxygen  obtained,  t  and  p  the  temperature  and 
pressure  under  which  it  was  measured,  a  the  aqueous 
tension  corresponding  to  £;  then  v,  the  volume  the 
gas  would  occupy  at  0°  and  760  mm.  pressure,  will  be 
equal  to 

273v(p  -  a)  ^ 

760(273+.$)  ' 

Having  found  F",  and  bearing  in  mind  that  1000  cc. 
of  oxygen  weighs  1.4298  grams  under  standard  condi- 
tions, we  can  readily  calculate  the  weight  of  the 
oxygen.  This  weight  should  be  the  same  as  that 
directly  determined. 

Next,  divide  the  weight  of  oxygen  by  the  weight  of 
the  chlorate  :  this  will  give  the  percentage  of  oxygen 
in  potassium  chlorate,  as  found  by  actual  experiment. 
This  should  of  course  be  the  same  in  each  case.  If 
we  assume  the  formula  KC1O3  for  potassium  chlorate, 
we  can  readily  calculate  the  percentage  of  oxygen 
which  the  salt  theoretically  contains.  The  molecular 

weight  of  the  chlorate  is  122.5  ;  of  this  v^^-^is  oxygen, 


or  39.18  per  cent. 

By  following  directions  carefully  and  performing 
the  weighings  with  accuracy,  you  will  generally  be 
able  to  find  the  percentage  to  within  two  tenths  ;  the 
indirect  method  —  by  volume  —  is  usually  more  accu- 
rate than  the  direct,  since,  if  the  tube  and  the  chlorate 
be  not  both  perfectly  dry,  some  moisture  will  pass 
over  with  the  oxygen  and  the  weight  of  the  oxygen 
found  by  difference  will  thus  be  too  large. 


THE  ATOMIC  WEIGHT  OF  ZINC. 


THE  ATOMIC  "WEIGHT  OF  ZINC. 
EXPERIMENT  51. 

Apparatus  shown  in  Fig.  22  ;  pure  zinc  ;  dilute  sulphuric  acid. 

Arrange  an  apparatus  as  shown  in  Fig.  22.  A  is  a 
flask  of  50-75  cc.,  closed  with  a  tight  rubber  stopper 
with  two  holes  :  through  one  passes  the  tube  by  which 
the  acid  in  the  reservoir  D  can  be  brought  in  contact 
with  the  zinc.  Its  lower  end  in  A  is  bent  upward  to 
prevent  any  hydrogen  escaping  into  D.  Through  the 


FIG.  22. 

other  hole  passes  the  delivery-tube  B,  its  lower  end 
being  just  even  with  the  bottom  of  the  cork.  At  B 
the  tube  is  drawn  out  slightly  and  a  plug  of  glass- 
wool  is  inserted  to  prevent  any  particles  of  zinc  being 
carried  over  into  C  without  being  dissolved. 

Weigh   off  very  carefully  0.10-0.13  gram    of  pure 
zinc  *  and  place  it  in  A.    Next  fill  D  with  water  which 

*  This  is  the  proper  amount  for  a  50-cc.  gas-measuring  tube  •.  a 
100-cc.  tube  will  of  course  permit  of  using  twice  as  much. 


48  THE  ATOMIC  WEIGHT  OF  ZING, 

EXPERIMENT  51— Continued. 

has  been  boiled  for  at  least  five  minutes  to  remove  all 
air,  and  is  still  hot.  When  the  stopper  has  been 
pushed  tight  into  place,  open  the  pinch-cock  E  and 
let  the  water  flow  through  the  apparatus  pushing  all 
air  ahead  of  it  and  through  B ;  see  that  no  bubbles 
are  left  in  A.  Let  the  water  in  D  sink  almost  to  the 
bottom,  taking  care,  however,  that  no  air  is  carried 
down  into  the  tube,  and  then  fill  with  dilute  sulphuric 
acid  (1 :  4)  which  has  also  been  thoroughly  boiled  and 
is  hot.  Fill  the  measuring-tube  C  with  hot  boiled 
water  and  invert  it,  as  shown  in  the  fig- 
ure, over  the  outlet  of  B. 

Now  admit  the  acid  by  opening  E. 
Hydrogen  will  be  formed  and  the  zinc 
dissolved  ;  if  the  action  slackens  warm  A 
with  the  burner-flame  and,  when  neces- 
sary, admit  more  acid.  When  the  zinc 
has  been  completely  dissolved,  fill  D,  as 
before,  with  hot  boiled  water  and,  by 
opening  E,  drive  all  gas-bubbles  out  of 
A  into  C.  If  now  the  apparatus  has  been 
carefully  prepared  and  the  directions  fol- 
lowed, you  have  in  C  a  weight  of  hydro- 
gen which  bears  to  the  weight  of  zinc  dis- 
solved the  ratio  borne  by  the  weight  of 
two  atoms  of  hydrogen  to  that  of  one 
FIG-  ^  atom  of  zinc. 

In  order,  knowing  the  volume  of  the  hydrogen,  to 
find  its  weight,  we  transfer  the  tube  C  to  a  large 
cylinder  of  water,  as  shown  in  Fig.  23.  This  is  done 
by  closing  the  mouth  of  C  with  the  thumb  or  by  slip- 
ping a  small  crucible  or  beaker  under  it,  to  prevent 


ITT  if  IV  B  RSI  T  7 If 

OXYGEN  FROM  MANGANESE  DIOXIDE.  49 

EXPERIMENT  51— Continued. 

the  contents  from  being  lost.  The  water  in  the  cylin- 
der should  have  been  drawn  sufficiently  long  before- 
hand for  it  to  have  come  to  the  temperature  of  the 
room.  Let  the  tube  stand  with  the  water  at  the  same 
level  inside  and  out,  for  about  half  an  hour.  Then 
read  the  volume  of  the  hydrogen  as  carefully  as  pos- 
sible, noting  the  temperature,  barometric  height,  and 
tension  of  aqueous  vapor.  By  means  of  the  formula 

V=         ^L L  calculate  the  volume  the  hydrogen 

7bO^J7o  -j—  tj 

would  occupy  at  0°  and  760  mm.  pressure.  Under 
these  conditions  a  litre  of  hydrogen  weighs  0.089578 
gram.  What  is  the  weight  of  the  hydrogen  obtained 
in  your  experiment  ?  What  ratio  does  it  bear  to  that 
of  the  zinc  ?  What  ratio  should  it  bear  ? 

THE  ACTION   OF    SULPHURIC  ACID    ON   SALT. 
EXPERIMENT  52. 

Test  tube,  common  salt;  concentrated  sulphuric  acid. 

Pour  2  or  3  cc.  concentrated  sulphuric  acid  on  a 
gram  or  two  of  common  salt  in  a  test-tube. 

What  takes  place  ?  Is  a  gas  formed  ?  If  so,  what 
is  its  appearance  ?  Has  it  an  odor  ?  Blow  across  the 
mouth  of  the  test-tube :  what  do  you  notice  ? 

The  gas  is  hydrochloric  acid. 

OXYGEN  FROM  MANGANESE   DIOXIDE    AND 
CONCENTRATED   SULPHURIC  ACID. 

EXPERIMENT  53. 

Flask;  glass  tubing;  pneumatic  trough;  cylinders  or  test- tubes,  gran- 
ulated manganese  dioxide,  concentrated  sulphuric  acid. 

1.  Fit  a  cork  bored  with  two  holes  to  a  flask  of 


50  CHLORINE. 

EXPERIMENT  53— Continued. 

about  150  cc.  capacity  ;  through  one  hole  fit  a  delivery- 
tube,  and  through  the  other  a  straight  tube  open  to 
the  air  but  dipping  below  the  level  of  the  acid  in  the 
flask.  Put  10-15  grams  of  granulated  manganese  di- 
oxide in  the  flask  and  pour  upon  it  enough  concen- 
trated sulphuric  acid  to  form  a  layer  about  1  cm.  (say 
\  inch)  deep.  [The  arrangement  of  the  steam-gen- 
erator in  Fig.  10,  Experiment  28,  is  about  what  is 
wanted.  The  second  tube — in  Fig.  10  a  funnel-tube — 
is  a  "  safety-tube "  to  prevent  water  from  the  tank 
being  drawn  back  through  the  formation  of  a  partial 
vacuum,  into  the  flask.] 

2.  On  heating  the  sulphuric  acid  to  near  its  boiling- 
point,  oxygen  is  evolved.     After  the  air  has  been  dis- 
placed, the  gas  is  practically  pure,  since  the  fumes  of 
the  acid  are  absorbed  by  the  water  through  which  the 
gas  bubbles  during  the  process  of  collecting  it.     Test 
the  gas  for  oxygen  in  the  usual  way. 

3.  As  soon  as  the  action  is  over,  either  withdraw 
the  cork  from  the  flask,  or  else  take  the  delivery-tube 
out  of  the  water  of  the  trough  :  this  is  to  prevent  any 
water  being  drawn  back  into  the  flask  as  it  cools.     Let 
the  flask  cool  thoroughly  before  attempting  to  pour 
out  its  contents. 

CHLOKINE. 
EXPERIMENT  54. 

Apparatus  shown  in  Fig.  24;  manganese  dioxide;  common  salt;  con- 
centrated sulphuric  acid;  sand-bath;  6  or  8  dry  cylinders;  anti- 
mony; Dutch  foil,  calico. 

In  a  flask  of  750-1000  cc.  capacity  mix  50  grams 
(1|— 2  ounces)  of  black  oxide  of  manganese  with  an 


CHLORINE. 


51 


EXPERIMENT  54— Continued. 

equal  weight  of  common  salt.  Pour  on  this  a  mixture 
of  120  grams  of  concentrated  sulphuric  acid  with  60 
grams  of  water,  which  has  been  allowed  to  cool.*  Ar- 
range the  apparatus  as  shown  in  Fig.  24,  setting  it  up 
under  a  hood.  Heat  gently  in  a  sand-bath. 
What  is  given  off  ? 


FIG.  24. 

Collect  six  or  eight  dry  cylinders  full  of  the  gas  by 
letting  the  delivery-tube  extend  to  the  bottom  of  the 
collecting  vessel  and  covering  the  mouth  with  a  piece 
of  paper.  You  can  see  when  the  vessel  is  full  by  the 
color  of  the  gas.  Do  not  inhale  the  gas.  Perform  the 
following  experiments  under  the  hood : 

1.  Into  one  of  the  vessels  containing  chlorine  shake 
a  little  finely  powdered  antimony. 

What  takes  place  ?  Antimony  trichloride,  SbCl3, 
is  formed. 


*  See  second  note,  Experiment  29. 


52  DECOMPOSITION  OF  CHLORINE -WATER. 

EXPERIMENT  54— Continued. 

In  what  respects  is  this  experiment  like  the  one  in 
which  iron  was  burned  in  oxygen  ? 

2.  Into  a  second  vessel  put  a  few  pieces  of  copper- 
foil  which   you   have   heated,  or,  better,  a  sheet   of 
"  Dutch  foil  "  or  copper-leaf.     What  takes  place  ? 

3.  Into  a  third  vessel  put  a  piece  of  paper  with  writ- 
ing on  it,  some  flowers,  and  some  pieces  of  colored 
calico  which  you  have  moistened.     What  takes  place  ? 

4.  Into  a  fourth  vessel  put  a  dry  piece  of  the  same 
calico  used  in  3. 

What  difference  is  there  in  the  action  of  the  chlorine 
on  the  dry  and  on  the  moist  calico  ? 

ABSTRACTION   OF   HYDROGEN   BY  CHLORINE. 
EXPERIMENT  55. 

Cylinder  of  chlorine    filter-paper,  oil  of  turpentine. 

Crease  lengthwise  a  strip  of  filter-paper  about  6 
inches  long  and  2-3  inches  wide.  Pour 
on  this  a  little  warm  oil  of  turpentine* 
and  quickly  introduce  it  into  a  cylinder 
of  chlorine.  What  is  the  result  ? 

DECOMPOSITION  OF  CHLORINE 
WATER. 

EXPERIMENT  56. 

Tube  shown  in  Fig.  25;  chlorine- water;  disk;  splin- 
ter of  wood. 

Seal  the  end  of  a   glass  tube,  say  a 

*  Oil  of  turpentine,  being  an  inflammable  liquid, 
should  be  heated  with  care  :  a  little  in  a  large  test 
.  85,          tube  is  probably  the  safest  method. 


HYDROCHLORIC  ACID.  53 

EXPEEIMENT  56— Continued. 

metre  (or  about  a  yard)  in  length  and  about  12  mm. 
(J  inch)  in  internal  diameter;  fill  this  with  a  strong 
solution  of  chlorine  in  water ;  invert  it,  as  shown  in 
Fig.  25,  in  a  shallow  dish  containing  some  of  the 
same  solution  of  chlorine  in  water.  Place  the  tube  in 
direct  sunlight.  What  takes  place  ?  What  change  in 
color  of  the  solution,  in  the  odor,  taste  ?  Examine  the 
gas  which  collects  at  the  top.  Is  it  oxygen  ? 

DIEECT  UNION  OF  CHLORINE  AND  HYDEOGEN. 
EXPERIMENT  57. 

Hydrogen-generator  with  tip  for  burning  the  gas">,  cylinder  of  chlo- 
rine. 

Into  a  jar  of  dry  chlorine  lower  a  flame  of  burning 
hydrogen.  [This  is  best  accomplished  by  bending  a 
tube  into  the  form  of  a  letter  J  and  providing  it  with 
a  tip  at  the  end  of  the  shorter  limb,  from  which  the 
gas  burns.]  What  change  does  the  flame  suffer? 
Why  ?  What  is  formed  ?  Blow  across  the  mouth  of 
the  cylinder  :  what  is  the  result  ?  Where  have  you 
met  with  this  phenomenon  before  ? 

HYDEOCHLOEIC  ACID. 
EXPEEIMENT  58. 

Apparatus  shown  in  Fig.  26  ;  common  salt ;  concentrated  sulphuric 
acid ;   filter ;   evaporating-dish  ;   arsenic-tube   or  test-tube ;  dry 
cylinders  ;   iron-filings  ;   granulated  zinc  ;    manganese   dioxide 
litmus-paper  ;  red  cabbage  ;  caustic-soda  solution. 

1.  Arrange  an  apparatus  as  shown  in  Fig.  26.  The 
flask  should  have  a  capacity  of  about  one  litre.  The 


54:  HYDROCHLORIC  ACID. 

EXPERIMENT  58— Continued. 

tubes  leading  into  the  Wolff's  bottles  must  not  dip  in 
the  water  in  the  bottles.  If  they  end  a  few  milli- 
metres above  the  surface  of  the  water  all  the  gas  will 
be  absorbed.  It  will  be  better  to  have  the  first 
Wolff's  bottle  not  more  than  a  quarter  full :  this  will 
ensure  your  obtaining  a  concentrated  solution.  It  is 
not  essential,  but  as  a  rule  better  results  are  obtained 
if  the  flask  be  heated  on  a  sand-bath.  Weigh  out, 


FIG.  26. 

separately,  50  grams  common  salt,  50  grams  concen- 
trated sulphuric  acid,  and  10  grams  water.  Mix  the 
acid  and  water,  taking  the  usual  precautions  (see  sec- 
ond note,  Experiment  29).  The  object  of  adding  the 
water  is  to  prevent  the  foaming  of  the  rather  viscous 
sulphuric  acid.  Let  the  mixture  cool  down  to  the 
ordinary  temperature,  and  then  pour  it  on  the  salt  in 
the  flask. 

2.  Heat  the  flask  gently ;  conduct  the  gas  at  first 
over  the  water  contained  in  the  Wolff's  flasks.  Does 
any  escape  being  completely  absorbed  in  the  first 
Wolff's  flask? 


HYDROCHLORIC  ACID.  55 

EXPERIMENT  58— Continued. 

What  does  the  fact  of  the  sinking  of  the  solution 
through  the  water  indicate  ? 

What  besides  the  visible  substances  is  contained  in 
all  the  vessels  at  the  beginning  of  the  experiment? 

3.  After  the  gas  has  passed  for  10  to  15  minutes 
disconnect  at  A  (see  Fig.  26).     What  appears  ? 

Blow  your  breath  on  the  gas  coming  out  of  the  tube, 
taking  care  not  to  direct  the  gas  towards  your  face, 
and  not  to  get  too  near  it.  What  effect  has  this  ? 

4.  Apply  a  lighted  match  to  the  end  of  the  tube. 
Does  the  gas  burn  ?  Does  the  match  continue  to  burn  ? 

5.  Collect   some   of   the   gas   in   each   of  two   dry 
cylinders,  as  in  the  case  of  chlorine,  cover  them  with 
glass  plates,   and  then  connect   the  generating-flask 
again  with  the  flasks  containing  the  water,  and  let  the 
action  continue  until  no  more  gas  is  given  off. 

6.  Turn  one  of  the  cylinders  mouth-downward  in 
the  water  of  the  pneumatic  trough  and  withdraw  the 
glass  plate.     Wliat  happens  ? 

What  observation  have  you  already  made  which 
shows  that  you  cannot  collect  this  gas  in  the  same 
way  that  you  collected  hydrogen  and  oxygen  ? 

In  collecting  chlorine  and  hydrochloric  acid  the 
vessels  must  stand  mouth-upward.  Are  these  gases 
heavier  or  lighter  than  air  ? 

Has  the  gas  any  color  ?     Is  it  transparent  ? 

7.  Insert   a  burning  stick  or  candle  in  the  other 
cylinder  filled  with  the  gas.     Does  the  gas  support 
combustion  ? 

Express  by  an  equation  the  action  which  takes  place 
in  the  preparation  of  hydrochloric  acid. 
What  is  left  in  the  flask  ? 


56  HYDROCHLORIC  ACID. 

EXPEEIMENT  58— Continued. 

8.  After  the  flask  lias  cooled  down  pour  hot  water 
on  the  contents  until  it  is  covered  2  or  3  inches  deep, 
shake  thoroughly  and,  when  the  water  has  dissolved 
as  much  as  it  will  of  the  substance,  filter ;  on  cooling, 
the  solid  product  will  be  deposited.      Pour  off  the 
liquid,  and  dry  the  solid  substance  by  placing  it  upon 
folds  of  filter-paper. 

9.  Compare  the  substance  with  the  common  salt 
which  you  put  into  the  flask  at  the  beginning  of  the 
experiment. — Heat  a  small  piece  of   each   in  a  dry 
tube. — Treat  a  small  piece  of  each  in  a  test-tube  with 
a  little  concentrated  sulphuric  acid. 

What  differences  do  you  observe  between  them  ? 
If  in  the  experiment  you  should  recover  all  the  so- 
dium sulphate  formed,  how  much  would  you  get  ? 

10.  Put  about  50  cc.  of  the  liquid  from  the  first 
Wolff's  bottle  in  a  porcelain  evaporating-dish  under  a 
hood,  and  heat  over  a  small  flame  just  to  boiling. 

Is  hydrochloric  acid  given  off? 

Can  all  the  liquid  be  driven  off  by  boiling  ? 

11.  Try  the  action  of  a  little  of  the  liquid  from  the 
first  Wolff's  bottle  on  a  gram  or  two  of  iron-filings  in 
a  test-tube. 

Is  a  gas  given  off  ?     What  is  it  ? 

12.  Add  a  little  of  the  liquid  to  a  gram  or  two  of 
granulated  zinc  in  a  test-tube. 

What  gas  is  given  off  ? 

13.  Add  a  little  to  a  gram  or  two  of  manganese 
dioxide  in  a  test-tube. 

What  is  given  off  ?     How  do  you  know  ? 

14.  Add  ten  or  twelve  drops  to  2  or  3  cc.  water  in  a 
clean  test-tube.     Taste  the  solution. 


PREPARATION  OF  POTASSIUM  CHLORATE.        57 

EXPERIMENT  58— Continued. 
How  would  you  describe  the  taste  ? 

15.  Add  a  drop  or  two  of  a  solution  of  Hue  litmus* 
or  put  into  it  a  piece  of  paper  colored  blue  with  lit- 
mus.    What  change  takes  place  ? 

To  the  solution  to  which  litmus  has  been  added  add 
a  drop  or  two  of  caustic  soda  or  ammonia.  What 
change  takes  place? 

16.  Steep  a  few  leaves  of  red  cabbage  in  water  ;  add 
a  few  drops  of  the  solution  thus  obtained  to  dilute 
hydrochloric  acid.     Is  there  a  change  of  color  ?     Try 
the    action    of   the    alkali  which  was  used  with  the 
litmus.     What  effect  does  it  produce? 

In  what  experiment  did  you  obtain  caustic  soda  ? 

Write  a  full  account  of  all  you  have  done  since  you 
started  with  the  sulphuric  acid  and  common  salt,  and 
be  sure  that  your  account  contains  answers  to  all  the 
questions  which  have  been  asked. 


PREPARATION   OF   POTASSIUM  CHLORATE. 
EXPERIMENT  59. 

Chlorine-generator;   beaker;   funnel;  caustic  potash;  arsenic-tube; 
concentrated  sulphuric  acid  ;  test-tubes. 

Dissolve  40  grams  (or  about  1J  ounces)  caustic 
potash  in  100  cc.  water  in  a  beaker,  warm  the  solu- 
tion, and,  under  a  hood,  pass  into  it  chlorine  from  a 
generator  containing  about  75  grams  of  salt  and  the 
other  constituents  in  proportion.  Arrange  an  inverted 
funnel  on  the  end  of  the  delivery-tube  so  that  the  edge 
of  the  funnel  just  dips  below  the  surface  of  the  potash 

*  Litmus  is  a  vegetable  substance  prepared  for  use  as  a  dye. 


58        PREPARATION  OF  POTASSIUM  CHLORATE. 

EXPEEIMENT  59—  Continued. 

solution.     This  is  to  prevent  the  choking  of  the  deliv- 
ery-tube by  the  formation  of  chlorate  crystals  in  it. 

Shake  or  stir  the  solution  constantly ;  when  a  strip 
of  pink  litmus-paper  dipped  in  the  solution  no  longer 
turns  blue,  but  is  bleached  instead,  the  reaction  is 
complete.  Next  heat  the  solution  which  now  contains 
a  mixture  of  potassium  chlorate  and  chloride,  filter  it 
while  hot,  and  set  aside  to  crystallize.  The  chlorate, 
being  much  less  soluble  in  cold  water  than  the  chlor- 
ide, is  deposited,  but  the  crystals  are  not  pure.  In 
order  to  separate  the  chloride  completely,  filter  the 
solution,  wash  the  crystals  on  the  filter  with  one  or 
two  cc.  of  cold  water,  then  dissolve  the  chlorate  in 
boiling-hot  water,  using  as  little  as  possible,  and  set 
aside  to  cool.  Evaporate  the  solution  of  chloride, 
from  which  the  chlorate  first  separated,  and  crystal- 
lize ;  recrystallize  from  a  little  hot  water.  Separate 
both  kinds  of  crystals  from  the  respective  mother- 
liquors  and  dry  on  layers  of  filter-paper. 

Chlorate. — Heat  some  of  the  salt  in  an  arsenic-tube  ; 
is  oxygen  given  off?  Treat  a  very  little  in  a  test-tube 
with  a  few  drops  of  concentrated  sulphuric  acid, 
holding  the  mouth  of  the  test-tube  away  from  the 
face  ;  what  happens  ?  Perform  the  same  experiments 
with  potassium  chlorate  from  the  laboratory  bottle ; 
are  the  two  identical  ? 

Chloride. — Heat  some  in  an  arsenic-tube  ;  is  oxygen 
given  off?  Treat  some  with  concentrated  sulphuric 
acid ;  what  gas  is  given  off?  Do  you  get  the  same 
gas  as  from  sodium  chloride  ?  Is  it  fair  then  to 
assume  that  any  chloride  will  give  this  gas  when 
treated  in  this  way  ? 


PREPARATION  OF  BLEACHING-POWDER. 


59 


EXPERIMENT  59—  Continued. 

Perform  the  same  experiments  with  potassium  chlor- 
ide from  the  laboratory  bottle  ;  are  they  identical  ? 

What  is  left  in  the  test-tube  after  the  chlorate  or 
the  chloride  has  been  treated  with  concentrated  sul- 
phuric acid? 

PKEPAKATION   OF  BLEACHING-POWDEK. 
EXPERIMENT  60. 

Chlorine-generator  ;  beaker  ;    funnel ;   quick-lime  ;  apparatus  shown 
in  Fig.  21 ;  concentrated  sulphuric  acid  ;  antimony,  etc. 

Weigh  off  into  an  evaporating-dish  or  large  beaker 
20-30  grams  (about  an  ounce)  of  good  quick-lime. 


Pour  upon  it  one  or  two  cc.  of  water  and  stir  it  up ; 
when  the  lime  has  become  very  hot,  add  a  little  more 
water,  and  so  on  until  the  lime  has  crumbled  to  a  fine 
dry  powder.  It  is  then  "  slaked."  Now  mix  it  with 


60  NEUTRALIZATION. 

EXPERIMENT  60—  Continued. 

water  to  form  a  thin  paste  and,  under  a  hood,  pass 
chlorine  into  it  as  into  the  potash  solution  in  the  last 
Experiment.  When  the  action  is  over  (see  last  Ex- 
periment) pour  the  paste  into  a  tflask  fitted  as  shown 
in  Fig.  27  ;  pour  upon  it  a  mixture  of  equal  parts  of 
concentrated  sulphuric  acid  and  water.  50  grams  of 
the  mixture  will  probably  suffice.  What  is  given  off? 
Is  it  chlorine  ?  Was  it  held  mechanically  by  the  lime, 
or  in  chemical  combination  ?  What  will  be  left  in  the 
flask  when  all  the  chlorine  is  driven  off?  Write  the 
reactions  which  have  taken  place,  beginning  with  the 
slaking  of  the  lime. 

NEUTRALIZATION. 
EXPERIMENT  61. 

2  Mohr  burettes  (50  cc.) ;  beakers  ;  flasks  ;  dilute  sulphuric,  nitric, 
hydrochloric  or  acetic  acid  ;  caustic  soda  ;  caustic  potash  ; 
litmus-solution. 

1.  Make  dilute  solutions  of  any  two  of  the  above- 
mentioned  acids  by  mixing  8  cc.  of  the  dilute  labora- 
tory-desk acid  with  400  cc.  of  water.  Make  dilute 
alkali  solutions. by  dissolving  2  grams  of  caustic  soda 
in  400  cc.  of  water  and  a  like  weight  of  caustic  potash 
in  the  same  amount  of  water.  Put  each  of  the  four 
solutions  in  a  flask  bearing  an  appropriate  label  and 
fitted  with  a  cork.  See  that  the  solutions  are  thor- 
oughly mixed.  Arrange  the  burettes  as  shown  in  Fig. 
28,  after  making  sure  that  they  are  clean  and  dry. 
Fill  one  with  one  of  the  alkali  solutions  and  the  other 
with  one  of  the  dilute  acids.  Let  the  liquid  flow  out 
of  each  burette  until  the  glass  tip  is  full ;  have  the 
burette  filled  to  the  zero- mark. 


NEUTRALIZA  TION. 


61 


EXPERIMENT  61— Continued. 

2.  Draw  off  now,  say,  15  cc.  of  the  acid  into  a  beaker 
by  opening  the  pinchcock  carefully  and  closing  when 
the  level  of  the  liquid  inside 

the  burette  has  fallen  to  the 
proper  point.  Add  a  little 
water  and  two  or  three  drops 
of  litmus-solution.  The  lit- 
mus will  turn  pink.  Now 
into  another  beaker  pour 
some  water  and  add  a  few 
drops  of  litmus  to  it ;  this  is 
your  "neutral  color,"  and  rep- 
resents the  color  the  litmus 
in  the  acid  solution  should 
assume  when  it  has  been  ex- 
actly neutralized.  The  in- 
tensity of  the  color  in  the  two 
beakers  should  be  as  nearly 
as  possible  the  same.  Next, 
to  the  acid  solution  add,  drop 
by  drop,  from  the  burette 
containing  the  solution  of  the 
alkali  until  the  neutral  point  is  reached.  If  you  should 
happen  to  add  too  much  alkali,  add  another  cc.  of 
acid  and  then  add  alkali  again  to  exact  neutralization. 
Read  off  now  the  respective  amounts  of  acid  and  alkali 
employed  and  calculate  the  ratio  of  their  strengths. 

3.  Repeat  the  experiment,  using  a  different  amount 
of  acid.     Do  you  get  the  same  result?     If  not,  try  it 
carefully  again  and  average  the  values  obtained ;  this 
will  give  you  pretty  accurately  the  relative  strength 
of  the  particular  solutions  you  have  compared. 


FIG.  28. 


62  NEUTRALIZATION. 

EXPEEIMENT  61 — Continued. 

4.  Now  change,  say,  the  alkali  (of  course  cleansing 
and  drying  the  burette),  and  in  the  same  manner  de- 
termine the  ratio  between  the  acid  and  the  second 
alkali.     By  comparing  the  figures  obtained  you  will 
know  just  how  much  of  each  alkali  solution  is  required 
to  neutralize  1  cc.  of  the  acid  and  hence  their  relative 
neutralizing  power.     Another   point   will   have   been 
brought  out  in  these  experiments  if  they  have  been 
conducted  carefully :  the  ratio  between  a  given  acid 
and  a  given  alkali  solution  is  independent  of  the  quan- 
tities employed  ;  the  dissolved  substance  is  perfectly 
uniformly  distributed  through  the  solution. 

5.  Next,  change  the  acid  and  compare  the  second 
acid  with  the  second  alkali. 

6.  Finally,  compare  the  second  acid  with  the  first 
alkali.     Tabulate  the  results.     It  will  be  found  that 
the  relative  neutralizing  powers  of  the  two  alkalies 
are  the  same  when  determined  by  means  of  the  second 
acid  as  by  the  first :  in  other  words  this  power  in  one 
base,   as  compared  with  that  in  another  base,  is  en- 
tirely independent  of  the  character  of  the  acid  used 
for  comparison.     The  ratio,  too,  remains  the  same  no 
matter  how  strong  or  how  weak  the  solution  of  acid 
may  be.     The  same  conclusion  will  of  course  be  found 
to  apply,  vice  versa,  to  the  relation  between  the  two 
acid  solutions. 


NEUTRALIZATION-FORMATION  OF  SALTS.       63 

NEUTRALIZATION—  FOKMATION  OF  SALTS. 
EXPERIMENT  62. 

Caustic  soda  ;    hydrochloric  acid  ;    litmus-paper  ;   evaporating-dish  ; 
water-bath;  nitric  acid;  arsenic-tube;  concentrated  sulphuric  acid. 

1.  Dissolve  5  grams  caustic  soda  in  50  cc.  water. 
Add  dilute  hydrochloric  acid  slowly,  examining  the 
solution  from  time  to  time  by  means  of  a  piece  of 
paper  colored  blue  with  litmus.     As  long  as  the  solu- 
tion is  alkaline  it  will  cause  no  change  in  the  color  of 
the  paper.     The  instant  it  passes  the  point  of  neutrali- 
zation it  changes  the  color  of  the  paper  red.     When 
this  point  is  reached,  evaporate  the  water  on  a  water- 
bath  to  complete  dryness,  and  see  what  is  left. 

Taste  the  substance.     Has  it  an  acid  taste  ? 

Does  it  suggest  any  familiar  substance  ? 

If  it  is  common  salt,  or  sodium  chloride,  how  ought 
it  to  conduct  itself  when  treated  with  concentrated 
sulphuric  acid  ? 

Does  it  conduct  itself  in  this  way  ? 

Is  the  substance  an  alkali  ?  Is  it  an  acid  ?  Is  it 
neutral ? 

Write  the  equation  representing  the  action. 

2.  Perform  the  same  experiment  as  under  1,  using 
dilute  nitric  acid  instead  of  hydrochloric  acid. — Com- 
pare the  product  with  sodium  nitrate  from  the  labora- 
tory bottle. 

Heat  a  small  specimen  of  each  in  an  arsenic-tube. 
What  takes  place  ? 

Treat  a  small  specimen  of  each  in  a  test-tube  with  a 
little  concentrated  sulphuric  acid  and  warm  gently. 
WThat  takes  place  ? 

Write  the  equation  representing  the  action. 

Write  an  account  of  the  process  of  neutralization. 


PROPORTION  OF  OXYGEN  IN  THE  AIR. 


PROPORTION  OF  OXYGEN  IN  THE  AIR. 
EXPERIMENT  63. 

Graduated  tube,  etc.,  represented  in  Fig.  29  ;  phosphorus*  ;  splinter 

of  wood. 

1.  Arrange  an  apparatus  as  in   Fig.   29.     The   in- 
verted tube  is  graduated  in  cubic  centimetres ;  any 
convenient   size   will    serve.     Fill   the    cylinder  with 
water  'which  has  been  drawn  long  enough  to  have 
come  to  the  temperature  of  the  room.     Enclose  nearly 
as  much  air  as  the  graduated  portion  of  the  tube  will 
hold ;  bring  the  level  of  the  water  to  the  same  point 
inside  the  tube  and  out.     Bead  the  volume  carefully 
and  note  the  pressure,  temperature,  and  aqueous  ten- 
sion. 

2.  Introduce,  on  the  end  of  a  wire,  a  piece  of  phos- 

phorus about  half  the  size  of  a  small 
marble  and  push  it  at  least  a  quarter 
of  the  way  up  the  tube.  The  phos- 
phorus should  have  been  trimmed  so 
that  fresh  surfaces  are  exposed  on  all 
sides. 

After  twenty-four  hours  withdraw 
the  phosphorus  and  note  whether 
it  fumes  in  the  air.  If  it  does  not, 
trim  the  outside  with  a  knife  and  re- 
insert it  into  the  tube.  If  there  is  any 
sign  of  fuming  in  the  air  enclosed  in 
the  tube,  the  phosphorus  must  be 
left  in  contact  with  it  again  to  make 
FIO.  29.  sure  that  all  oxygen  shall  be  removed. 

*  See  second  note,  Experiment  20. 


NITROGEN.  05 

EXPERIMENT  63—  Continued. 

(Phosphorus  left  under  these  circumstances  in  contact 
\vith  air,  frequently  becomes  coated  with  the  products 
of  oxidation  to  such  an  extent  that  it  ceases  to  absorb 
oxygen.) 

3.  When  the  oxygen  has  been  completely  removed, 
the  phosphorus  is  withdrawn,  the  tube  lowered  to  ob- 
tain equal  pressure  within  and  without,  and  the  vol- 
ume, pressure,  temperature  and  aqueous  tension  again 
noted. 

4.  The  two  gas-volumes  have  probably  been  read 
under  different  conditions  of  temperature  and  pres- 
sure ;  they  are  therefore  not  comparable.     To  render 
them  so,  we  can  do  either  one  of  two  things :  (1)  we 
can  reduce  both  observed  volumes  to  "  standard  condi- 
tions," or  (2)  we  can  reduce  one  to  the  conditions  of 
the  other.     Provided  the'  conditions  are  the  same,  it 
makes  no  difference  what  they  are.     Bead  those  pro- 
portions of   the   text-book    relating   to   gas-measure- 
ments, reduce  the  volumes  to   the  same  conditions, 
and  determine  accurately  their  true  ratio.     What  per- 
centage of  the  air  is  oxygen  ? 

5.  Kernove  the  tube,  keeping  the  mouth  closed,  re- 
verse it,  and  introduce  a  burning  taper.     Is  the  resid- 
ual gas  oxygen  ?     Is  it  air  ? 

NITROGEN. 
EXPERIMENT  64. 

Bell- jar  ;  small  porcelain  crucible  fastened  on  a  flat  cork  ;  trough  ; 
bit  of  candle  ;  phosphorus  *  ;  sulphur. 

1.  Place  a  bell-jar  over  water  in  a  larger  vessel  of 
*  See  second  note,  Experiment  20. 


66  WATER -VAPOR  IN  THE  AIR. 

EXPEEIMENT  64—  Continued. 

water.  In  the  middle  of  a  flat  cork  about  three  inches 
in  diameter  fasten  a  small  porcelain  crucible,  and  float 
this  on  the  water  in  the  trough.  Put  in  it  a  piece  of 
phosphorus  about  twice  the  size  of  a  pea,  and  set  fire 
to  the  phosphorus.  Quickly  place  the  bell-jar  over  it 
on  a  support  which  will  prevent  the  jar  from  sinking 
more  than  an  inch  or  two  in  the  water. 

Why  is  air  at  first  forced  out  of  the  vessel  ? 

Why  does  the  water  afterward  rise  in  the  vessel  ? 

After  the  burning  has  stopped  and  the  vessel  has 
cooled  down,  about  what  proportion  of  the  air  is  left 
in  the  vessel  ? 

2.  Cover  the  mouth  of  the  bell-jar  with  a  glass  plate 
and  turn  it  mouth  upward.     Try  the  effect  of  intro- 
ducing one  after  the  other  several  burning  bodies  into 
the  gas,  as,  for  example,  a  candle,  a  piece  of  sulphur, 
etc. 

Explain  all  that  you  have  seen. 

3.  If  convenient,  place  a  live  mouse  in  a  trap  in  a 
bell-jar  over  water.     When  the  oxygen  is  used  up  the 
mouse  will  die.     After  the  animal  gives  plain  signs  of 
discomfort,  it  may  be  revived  by  taking  away  the  bell- 
jar  and  giving  it  a  free  supply  of  fresh  air. 

WATER- VAPOR  IN  THE  AIR. 
EXPEEIMENT  65. 

Watch-glass  ;  dry  calcium  chloride. 

On  a  watch-glass  expose  a  few  pieces  of  calcium 
chloride  to  the  air.  What  change  takes  place,  and 
how  is  this  explained  ?  See  Experiment  42.  (What 
is  a  substance  called  which  has  the  power  to  take  up 
water  from  the  air  ?) 


REMOVAL  OF  CARBON  DIOXIDE  FROM  THE  AIR.    67 


CARBON  DIOXIDE   IN  THE  AIK. 
EXPERIMENT  66. 

Quick-lime  ;  bottle  ;  beaker  ;  filter. 

1.  Slake  about   20  grams   quick-lime  (see  Experi- 
ment 60) ;  put  it  in  a  bottle,  nearly  fill  with  water 
and,  after  shaking  thoroughly,  filter  a  little   of  the 
lime-water   thus   prepared   into   a   beaker.      Set   the 
bottle  aside  for  the  insoluble  residue  to  settle. 

Expose  the  beaker  of  linie-water  to  the  air.  What 
happens  ?  To  what  is  this  due  ? 

2.  Repeat   the   experiment,   using   a  little   baryta- 
water  in  place  of  lime-water. 

KEMOVAL   OF   CARBON  DIOXIDE   FROM   THE 

AIR. 

EXPERIMENT  67. 

Apparatus  shown  in  Fig.  30  ;  solution  of  caustic  soda  ;  liine-water  or 

baryta-water. 

1.  Arrange  an  apparatus  as  shown  in  Fig.  30.  The 
wash-cylinders  A  and  B  are  half-filled  with  ordinary 
caustic  soda  solution;  they  may  be  replaced  by  U- 
tubes  as  described  in  Experiment  31,  if  it  prove  con- 
venient to  do  so.  The  bottle  C  is  filled  with  water. 
The  tube  D  reaches  to  the  bottom  of  the  bottle  ;  being 
filled  with  water  and  provided  with  a  pinchcock,  it 
acts  as  a  siphon.  Open  the  pinchcock — one  regulated 
by  a  screw  is  best — and  let  the  water  flow  slowly  out 
of  the  bottle ;  as  it  flows  out,  air  will  be  drawn  in 
through  the  caustic  soda  solution  in  A  and  B.  When 
the  bottle  has  been  a  quarter  filled  with  air,  take  out 
the  cork  and  fill  the  bottle  with  water  to  the  top. 
Beplace  the  stopper  and  again  let  the  air  be  drawn  in, 


68   PRODUCTION  OF  CARBON  DIOXIDE  IN  THE  AIR. 

EXPERIMENT  67—  Continued. 

this  time  until  the  bottle  is  filled.  The  air  first  drawn 
in  had  not  been  thoroughly  washed  and  hence  was 
not  used. 

2.  Now  remove  the  stopper  from  the  bottle,  pour  in 
20-30  cc.  clear  lime-water  or  baryta-water,  and  cork 


FIG.  30. 


the  bottle.     Shake  it  thoroughly.     Does  a  crust  form 
on  the  water  ?     Why  ? 

Keep  the  bottle  just  as  it  is  for  the  next  Experi- 
ment. 


PRODUCTION  OF  CARBON  DIOXIDE  IN  THE  AIR. 
EXPERIMENT  68. 

Same  apparatus  as  in  Experiment  67  ;  splinter  of  wood. 
Into  the  bottle  containing  air  from  which  the  carbon 
dioxide  has  been  removed,  insert  a  burning  stick  for 
a  moment.     Cork  the  bottle  again  and  shake  it.     Is 


REMOVAL   OF  WATER -VAPOR  FROM  THE  AIR.     69 

EXPERIMENT  68 — Continued. 

a  crust  formed  ?  Wood  contains  carbon.  What 
changes  will  have  taken  place  in  the  gases  within  the 
bottle  through  the  introduction  of  the  burning  stick  ? 
What  ones  were  there  originally?  What  ones  are 
there  now  ? 


REMOVAL   OF   WATER- VAPOR   FROM   THE   AIR. 
EXPERIMENT  69. 

Apparatus  shown  in  Fig.  31  ;  concentrated  sulphuric  acid  ;  dry  cal- 
cium chloride. 

Arrange  an  apparatus  as  shown  in  Fig.  31.  The 
bottle  A  contains  air ;  instead  of  fitting  it  with  the 
funnel-tube  it  is  probably  better  to  connect  it  direct 


FIG.  31. 


with  the  water-tap ;  this  will  enable  you  to  control 
better  the  flow  of  the  water.  The  cylinder  B  contains 
concentrated  sulphuric  acid  ;  if  desired,  it  may  be  re- 
placed by  a  U-tube.  C  must  be  carefully  dried,  after 


70  AMMONIA. 

EXPERIMENT  69 — Continued. 

which  a  few  pieces  of  calcium  chloride  are  put  into  it. 
Now,  by  allowing  water  to  flow  into  A,  force  the  air 
in  that  vessel,  which  is  of  course  saturated  with  mois- 
ture, slowly  through  B  into  (7.  Does  the  calcium 
chloride  grow  moist  ?  What  has  become  of  the  water- 
vapor  ? 

AMMONIA. 
EXPERIMENT  70. 

Ammonium  chloride  ;    watch-glass  ;    caustic  soda  ;   caustic  potash  ; 
quick-lime. 

1.  To  a  little  ammonium  chloride  on  a  watch-glass 
add  a  few  drops  of  a  strong  solution  of  caustic  soda, 
and  notice  the  odor  of  the  gas  given  off. 

2.  Do  the  same  thing  with  caustic  potash. 

3.  Mix  a  gram  of  quick-lime  and  a  gram  of  ammo- 
nium chloride  in  a  mortar,  and  notice  the  odor. 

Has  ammonium  chloride  this  odor  ? 
What  is  the  substance  with  the  odor  ?     What  is  its 
physical  condition  ? 

EXPERIMENT  71. 

Apparatus  described  below  ;  quick-lime  ;  ammonium  chloride  ;  sand- 
bath  ;  dry  cylinders  ;  splinter  of  wood  ;  pneumatic  trough. 

1.  Arrange  an  apparatus  as  shown  in  Fig.  26,  Ex- 
periment 58,  omitting  however  the  funnel-tube ;  a 
one-hole  stopper  will  therefore  suffice.  A  round- 
bottomed  flask  is  preferable  though  not  essential. 
Following  the  directions  given  in  Experiment  60, 
slake  100  grams  of  good  quick-lime,  taking  care  not 
to  add  more  water  than  is  necessary  to  cause  it  to 
crumble  to  a  fine  dry  powder.  Transfer  this  to  the 
flask  while  it  is  still  hot,  add  50  grams  of  ammonium 


AMMONIA. 


n 


EXPEKIMENT  71—  Continued. 

chloride,  shake  them  thoroughly  together,  and  con- 
nect at  once  with  the  delivery-tube.  Heat  the  mix. 
ture  on  a  sand-bath.  After  the  air  is  driven  out  the 
gas  will  be  completely  absorbed  in  the  first  Wolff's 
flask.  The  solution  of  ammonia  in  water  is,  however, 
lighter  than  water  itself  and  will  therefore  float  as  a 
layer  on  the  surface.  On  this  account  it  is  necessary 
occasionally  to  shake  the  Wolff's  flasks  to  make  the 
liquids  mix. 

2.  As  soon  as  the  gas  is  seen  to  be  absorbed  in  the 
water  in  the  first  flask,  disconnect  at  A,  and  connect 
with  another  tube  bent  upward.     Collect  a  cylinder 
or  bottle  full  of  the  escaping  gas  by  displacing  air, 
placing  the  vessel  with  the  mouth  doivmvard,  as  the  gas 
is  much  lighter   than  air.     The    ar- 
rangement is  shown  in  Fig.  32.     The 

tube  through  which  the  gas  enters 
the  vessel  should  pass  through  a 
piece  of  thick  paper  or  of  thin  card- 
board, and  this  should  rest  against 
the  mouth  of  the  vessel.  The  object 
of  this  is  to  prevent  currents  of  air 
from  carrying  the  gas  out  of  the  ves- 
sel. You  can  determine  when  the 
vessel  is  full  of  gas  by  the  strong 
smell  of  the  gas.  In  working  with  the 
gas  great  care  must  be  taken  to  avoid 
breathing  it  in  any  quantity.  The 
vessel  in  which  the  gas  is  collected  FlG-  32- 

should  be  dry,  as  water  absorbs  ammonia  very  readily. 
Hence  also  the  gas  cannot  be  collected  over  water. 

3,  As   soon   as   the   cylinder   or   bottle   is   full   of 


72  AMMONIA  ACTS  AS  A  BASE. 

EXPERIMENT  71 — Continued. 

gas,  place  it  mouth-downward  on  a  glass  plate,  fill 
a  second  cylinder  in  the  same  way,  then  connect  the 
delivery-tube  with  the  series  of  Wolff's  flasks  and 
pass  the  gas  over  the  water  as  long  as  it  is  given 
off.  Save  the  solution  and  label  it  ammonia.  It  is 
this  solution  which  is  used  under  the  name  ammonia 
in  the  laboratory. 

4.  Place  one  of  the  cylinders  mouth-downward  in 
the  water  of  a  pneumatic  trough  and  remove  the  glass 
plate.     What  happens  ?     What  does  this  show  ? 

5.  Into  the  other  cylinder  of  ammonia  introduce  a 
burning  stick.     Does  the  gas  burn  ?     Does  it  support 
combustion  ? 

AMMONIA  ACTS  AS  A  BASE. 

EXPEEIMENT   72. 

Evaporating-dish  ;  dilute  ammonia  ;  dilute  hydrochloric  acid  ;  litmus- 
paper  ;  water-balk. 

Pour  100  cc.  dilute  ammonia  solution  into  an  evap- 
orating-dish.  Try  its  effect  on  pink  litmus-paper. 
Now  add  hydrochloric  acid,  drop  by  drop,  until  the 
alkaline  reaction  is  destroyed  and  the  solution  is 
neutral.  Evaporate  to  dry  ness  on  the  water-bath. 
Compare  the  substance  thus  obtained  with  sal-am- 
moniac, or  ammonium  chloride.  Taste  them.  Heat 
them  on  a  piece  of  platinum  foil  or  in  a  clean  evap- 
orating-dish.  Treat  them  with  a  caustic  alkali.  Treat 
each  with  a  little  concentrated  sulphuric  acid  in  a  dry 
test-tube. 

Do  they  appear  to  be  identical  ?  How  do  they  act 
in  each  case?  Write  the  equations  expressing  the 
yarious  reactions, 


FORMATION  OF  NITRIC  ACID.  73 

DIRECT   COMBINATION   OF  AMMONIA   WITH 
ACIDS. 

EXPERIMENT  73. 

Cylinders  ;  apparatus  for  producing  ammonia  and  hydrochloric  acid. 

1.  Fill  two  dry  cylinders,  one  with  ammonia  and 
the  other  with  hydrochloric  acid  gas.     For  this  pur- 
pose, ii  you  have  no  suitable  generators  set  up,  the 
following  method  is  a  good  one  :  Provide  a  wide  test- 
tube  with  a  cork  and  delivery-tube.    Fill  it  half-full  of 
concentrated  hydrochloric  acid  and  warm  it  gently. 
Collect  the  gas  as  usual,  covering  the  cylinder  with  a 
glass  plate.     Empty,  wash  and  re-fill  the  test-tube, 
this  time  with  concentrated  ammonia  solution  ;  warm 
slightly  and  collect  the  gas  in  an  inverted  cylinder. 
Close  with  a  plate. 

2.  Now  bring  the  two  cylinders  together,  draw  out 
the  two  cover-plates  and  let  the  gases  mix.     What 
happens  ?     What  is  the  substance  ?     Can  you  notice 
any  evolution  of  heat  ? 

FORMATION  OF   NITRIC   ACID. 
EXPERIMENT  74. 

Retort  and  receiver  ;  Chili  saltpetre  ;  concentrated  sulphuric  acid. 

Arrange  an  apparatus  as  shown  in  Fig.  33.  In  the 
retort  put  40  grams  sodium  nitrate  (Chili  saltpetre) 
and  20  grams  concentrated  sulphuric  acid. 

On  gently  heating,  nitric  acid  will  distil  over  and  be 
condensed  in  the  receiver. 

After  the  acid  is  all  distilled  over — the  retort  will 
then  have  become  filled  with  deep  red  fumes — let  the 
retort  cool  a  little  ancl  then  pour  into  it  aJ2ojj£200  ccf 


74  CONCENTRATION  OF  NITRIC  ACID. 

EXPERIMENT  74—  Continued. 

of  hot  water.  Shake  thoroughly,  pour  off  through  a 
filter  and  crystallize.  Show  whether  the  salt  obtained 
is  sodium  sulphate  or  not. 


FIG.  33. 

The  acid  obtained  is  very  strong  and  may  be  used 
for  Experiments  76  and  77. 

CONCENTRATION   OF   NITRIC  ACID.* 
EXPERIMENT  75. 

400-500  cc.  retort ;  receiver  ;  concentrated  sulphuric  and  nitric  acids. 
Into  a  vessel  containing  100  grams  ordinary  concen- 
trated nitric  acid  pour  200  grams  concentrated  sul- 
phuric acid,  and  stir.  Distil  the  mixture  very  slowly, 
using  a  burner  turned  down  low.  This  is  necessary 
to  prevent  the  sulphuric  acid  distilling  with  the  nitric. 
The  acid  thus  obtained  is  called  "  fuming  "  nitric  acid  ; 
it  may  be  used  in  Experiments  76  and  77. 

*  Commercial  concentrated  nitric  acid  generally  contains  water  to 
f;he  extent  of  about  one-third  its  weight, 


NITRIC  ACID  AS  AN  OXIDIZING  AGENT.         75 

NITRIC   ACID   AS  AN   OXIDIZING  AGENT. 
EXPERIMENT  76. 

Test-tube  ;  carbon  stick  ;  fuming  nitric  acid. 

Under  a  hood  pour  the  concentrated  nitric  acid 
obtained  in  either  of  the  last  two  Experiments  into  a 
wide  test-tube,  filling  it  about  one-half  full.  Fix  the 
test-tube  in  a  clamp,  as  shown  in  Fig.  34,  warm  it  with 
the  burner  until  the  acid  is  hot,  and  then  lower  it  into 


FIG  34. 


a  beaker,  as  shown  in  the  figure.  The  beaker  is  to 
catch  the  acid  in  case  the  test-tube  should  break. 
Now  heat  the  end  of  a  stick  of  charcoal  until  it  glows, 
then  lower  it  carefully  into  the  test-tube*  until  it  just 
dips  below  the  surface  of  the  acid. — See  the  Figure. 

What  evidence  have  you  of  the  oxidizing  power  of 
the  acid  ?     Do  not  inhale  the  gases. 

*  If  it  touch  the  sides  the  tube  may  break. 


76          SOLUTION  OF1  METALS  IN  NITRIC  ACID. 

EXPERIMENT  77. 

Same  apparatus  as  in  Experiment  76  ;  fuming  nitric  acid  ;  horse-Lair. 

Into  the  mouth  of  the  test-tube  used  iu  Experiment 
76  and  still  containing  the  very  concentrated  nitric 
acid,  push  a  loose  plug  of  horse-hair. 

Raise  the  tube  and  clamp  until  they  are  above  the 
beaker.  Now  heat  the  acid  carefully  and  let  it  boil 
quietly. 

What  successive  changes  take  place  in  the  horse- 
hair? What  is  the  final  result?  What  change  do 
you  notice  in  the  acid  ? 

EXPERIMENT  78. 

Small  flask  ;  tin  ;  concentrated  nitric  acid. 

In  a  small  flask  put  a  few  pieces  of  granulated  tin ; 
pour  on  this  just  enough  ordinary  concentrated  nitric 
acid  to  cover  it.  [If  the  acid  obtained  in  Experiments 
74  and  75  be  used,  it  will  generally  be  found  without 
action  on  the  tin.  It  may  indeed  often  be  boiled 
without  in  any  way  affecting  the  metal.  Addition  of 
a  few  drops  of  water  will  then,  however,  start  a 
vigorous  action.]  If  action  does  not  begin  at  once, 
warm  the  acid.  What  is  the  solid  formed?  Is  it  a 
salt  of  nitric  acid  ?  Was  the  action  of  the  nitric  acid 
in  Experiments  76  and  77,  salt-formation  ?  In  Experi- 
ment 12  ?  In  Experiment  62  ? 

SOLUTION   OF   METALS   IN  NITRIC  ACID. 
EXPERIMENT  79. 

Flask  or  beaker  ;  concentrated  nitric  acid  ;  copper  foil  or  turnings  ; 
evaporating-disli ;  arsenic-tube  ;  concentrated  sulphuric  acid. 

Under  a  hood  dissolve  a  few  pieces  of  copper  foil, 
or  half  a  handful  of  copper  turnings,  in  ordinary  con- 


SOLUBILITY  OF  NITRATES  IN  WATER.  W 

EXPERIMENT  79—  Continued. 

centrated  nitric  acid  diluted  with  about  half  its 
volume  of  water.  When  the  copper  nas  disappeared, 
pour  the  blue  solution  into  an  evaporating-dish,  and 
evaporate  down  to  crystallization.  Compare  the  sub- 
stance thus  obtained  with  copper  nitrate. 

Heat  a  specimen  of  each  in  an  arsenic-tube.  Treat 
a  small  specimen  of  each  with  concentrated  sulphuric 
acid  in  a  test-tube.  What  change  in  color  takes  place 
on  warming  ?  Why  ?  Does  addition  of  water  restore 
the  color? 

ACTION  OF  HEAT  ON  NITRATES. 
EXPERIMENT  80. 

Arsenic-tubes;  nitrates  of  potassium,  sodium,  lead,  etc. 

In  a  clean  dry  arsenic-tube  heat  a  little  potassium 
nitrate  ;  what  change  do  you  notice  ?  Is  a  gas  given 
off?  Has  it  a  color  ?  Is  it  oxygen? 

Do  the  same,  using  sodium  nitrate  ;  are  the  results 
similar? 

Do  the  same  thing  with  some  powdered  lead  nitrate: 
is  the  gas  colored  ?  Does  it  contain  oxygen  ?  How 
do  you  know  ?  What  is  the  appearance  of  the  resi- 
due? How  does  it  differ  from  that  obtained  with 
potassium  nitrate  ? 

The  reactions  are  : 


(b)  Pb(N03)2  =  PbO  +  2NO3  +  O. 

SOLUBILITY  OF  NITRATES  IN  WATER. 

EXPERIMENT  Hi. 

Test-tubes;  potassium,  sodium,  copper,  and  lead  nitrates. 
Test  the  solubility  of  the  above-mentioned  nitrates 


78  NITROUS  ACID  AND  NITRITES. 

EXPERIMENT  81—  Continued. 

in  cold  water ;  in  hot  water.  Are  any  of  them  deli- 
quescent ?  Do  any  of  them  crystallize  with  water  of 
crystallization  ? 

NITRIC  ACID  REDUCED  TO  AMMONIA. 
EXPERIMENT  82. 

Test-tube;  evaporating-dish;  water-bath;  dilute  sulphuric  acid;  gran- 
ulated zinc;  dilute  nitric  acid;  caustic  soda  solution;  litmus-paper. 

In  a  good-sized  test-tube  treat  a  few  pieces  of  gran- 
ulated zinc  with  dilute  sulphuric  acid :  what  is 
evolved?  Now  add,  drop  by  drop,  dilute  nitric  acid. 

After  the  action  has  been  allowed  to  progress  for  a 
minute  or  two,  pour  the  contents  of  the  tube  into  an 
evaporating-dish,  place  this  on  the  water-bath  and 
evaporate  to  dryness.  What  has  become  of  the  zinc  ? 
Put  the  residue  into  a  test-tube  and  add  caustic  soda 
solution,  warm  and  see  if  ammonia  is  given  off.  Can 
you  smell  it  ?  Hold  a  strip  of  rnoist  pink  litmus-paper 
in  the  opening  of  the  test-tube :  what  effect  is  pro- 
duced ?  Dip  a  clean  glass  rod  in  dilute  hydrochloric 
acid  and  then  hold  it  in  the  mouth  of  the  tube  :  what 
do  you  notice  ?  To  what  is  this  effect  due  ?  Do  the 
same  using  dilute  nitric  acid :  is  the  effect  the  same  ? 
What  has  been  formed  ? 

NITROUS  ACID  AND  NITRITES. 
EXPERIMENT  83. 

Iron  pan  ;  potassium  nitrate  ;  metallic  lead  ;  concentrated  sulphuric 

acid. 

Heat  together  in  a  shallow  iron  pan  25  grams  po- 
tassium nitrate  and  50  grams  metallic  lead.  When 


MTltOtfS  OXIDE.  Y9 

EXPERIMENT  83— Continued. 

both  are  melted,  stir  them  together  as  thoroughly  as 
possible,  until  at  any  rate  most  of  the  lead  has  been 
converted  into  the  yellowish-brown  oxide.  Let  the 
mass  cool  down  and  then  pour  upon  it  in  successive 
portions  about  100  cc.  of  boiling-hot  water  ;  after  each 
portion  has  dissolved  as  much  as  it  will  pour  it  upon 
a  filter.  What  has  gone  into  solution  ?  How  was  the 
oxide  of  lead  formed  ?  Add  a  little  concentrated  sul- 
phuric acid  to  the  filtrate:  what  happens?  Do  the 
same  with  a  dilute  solution  of  potassium  nitrate :  what 
result  ? 

NITKOUS  OXIDE. 
EXPERIMENT  84. 

Retort  of  3-4  oz.  capacity;  crystallized  ammonium  nitrate;  wide  rub- 
ber tube;  cylinders;  candle  on  wire;  bits  of  wood;  phosphorus;* 
deflagrating-spoon . 

1.  In  a  retort  heat  10-15  grams  crystallized  ammo- 
nium nitrate  until  it  has  the  appearance  of  boiling. 
Do  not  heat  higher  than  is  necessary  to  secure  a  reg- 
ular evolution  of  gas.     Connect  a  wide  rubber  tube 
directly  with  the  neck  of  the  retort,  and  collect  two  or 
three  bottles  full  of  the  gas  over  water,  as  in  the  case 
of  oxygen. 

What  chemical  change  has  taken  place  ? 

2.  Insert  into  the  gas  a  piece  of  burning  wood,  a 
burning  candle,  a  bit  of  burning  phosphorus  in  a  de- 
flagrating-spoon. 

Explain  what  takes  place.  Could  you  distinguish 
the  gas  from  oxygen  ?  How  ?  What  is  left  in  a  jar 
in  which  a  piece  of  wood  has  been  burning  in  nitrous 

*  See  second  note,  Experiment  20. 


80  NITRIC  OXIDE. 

EXPEEIMENT  84— Continued. 

oxide?  What  is  left  when  phosphorus  has  been 
burned  in  nitrous  oxide  ?  How  could  you  distinguish 
the  gas  from  ordinary  air  ? 

NITRIC  OXIDE. 
EXPERIMENT  85. 

•Apparatus  shown  in  Fig.  35;  copper-foil  or  turnings;  ordinary  con- 
centrated nitric  acid;  cylinders. 

Arrange  an  apparatus  as  shown  in  Fig.  35.  In  the 
flask  put  a  few  pieces  of  copper-foil  one 
or  two  inches  long  by  about  half  an  inch 
wide,  or  else  a  handful  of  copper  turn- 
ings. Cover  this  with  water.  Now  slowly 
add  ordinary  concentrated  nitric  acicl. 
When  enough  acid  has  been  added  gas 
will  be  given  off.  If  the  acid  is  added 
quickly  it  not  infrequently  happens  that 
the  evolution  of  gas  takes  place  too  rap- 
idly, so  that  the  liquid  is  forced  out  of 
the  flask  through  the  funnel-tube.  This 

FIG.  35.          can  fog  avoided  by  not  being  in  a  hurry. 

What  is  the  color  of  the  gas  in  the  flask  at  first  ? 

What  is  it  after  the  action  has  continued  for  a  short 
time  ?  Explain  the  difference. 

Collect  over  water  several  cylinders  full  for  the  next 
two  experiments. 

Do  not  inhale  the  gas.  Perform  the  experiments  with 
nitric  oxide  where  there  is  a  good  draught. 

EXPERIMENT  83. 

Vessels  filled  with  nitric  oxide  in  last  experiment ;  splinter  of  wood. 
1.  Under  a  hood  turn  one  of  the  vessels  containing 


ANALYSIS  OF  NIT&IC  OXIDE.  81 

EXPERIMENT  86—  Continued. 

colorless  nitric  oxide  with  the  mouth  upward  and  un- 
cover it. 

What  takes  place  ?     What  is  the  new  product? 

Explain  the  appearance  of  the  colored  gas  in  Exper- 
iment 85,  and  the  fact  that  it  afterward  disappeared. 

What  was  in  the  vessel  at  the  beginning  of  the  op- 
eration ? 

2.  Into  one  of  the  vessels  containing  nitric  oxide 
insert  a  burning  stick.  Does  the  gas  burn  ?  Does  it 
support  combustion  ? 

ANALYSIS  OF  NITKIC  OXIDE. 
EXPERIMENT  86«.  • 

Cylinder  ;  cork  ;  deflagrating-spoon  ;  phosphorus  ;  pneumatic  trough  ; 
glass  plate  ;  cylinder  or  bottle  of  nitric  oxide. 

Fit  a  cylinder  with  a  close-fitting  cork.  Through 
the  cork  pass  the  wire  of  a  deflagrating-spoon  so  that 
when  the  cork  is  in  place  the  bowl  of  the  spoon  will 
be  in  the  middle  and  near  the  bottom  of  the  cylinder. 
See  that  the  cork  can  be  made  to  lit  air-tight  when 
pushed  into  place. 

Now  fill  the  cylinder  with  nitric  oxide  ;  *  close  it 
with  a  glass  plate  and  stand  it  mouth  up.  Place  a 
small  piece  of  phosphorus  t  in  the  spoon,  light  it,  and, 
removing  the  glass  plate  from  the  cylinder,  insert  the 
spoon  and  push  the  cork  down  tight.  Does  the  phos- 
phorus continue  to  burn  ?  Where  does  the  oxygen 
come  from  ?  What  will  the  residue  in  the  cylinder 
consist  of  ? 

As  soon  as  the  phosphorus  has  been  extinguished, 

*  See  Experiment  6. 

f  See  second  note,  Experiment  20. 


82  V8B  OF  CHARCOAL  FOR  FILTERING 

EXPERIMENT  860—  Continued. 

transfer  the  cylinder  at  once  to  a  pneumatic  trough 
and,  while  the  mouth  of  the  vessel  is  below  the  sur- 
face of  the  water,  withdraw  the  cork.  What  happens  ? 
How  much  gas  is  left  ?  Is  the  gas  nitrogen  ?  Try  it. 
What  are  the  volume-relations  between  oxygen  and 
nitrogen  in  nitric  oxide  ? 

USE   OF   CHARCOAL  FOE  FILTERING. 
EXPERIMENT  87. 

Funnel  8  to  4  inches  in  diameter  at  mouth  ;  filter  ;  bone-black  ;  solu- 
tion of  indigo  ;  solution  of  litmus  ;  flasks. 

1.  Make  a  filter  of   bone-black  by  fitting  a  paper 
filter  into  a  funnel  8  to  10  cm.  (3  to  4  inches)  in  diame- 
ter at  its  mouth,  and  half-filling  this  with  bone-black. 
Pour  a  dilute  solution  of  indigo  *  through  the  filter. 

What  effect  does  this  have  on  the  color  of  the  solution? 

2.  Do  the  same  thing  with  a  dilute  solution  of  lit- 
mus.— If  the  color  is  not  completely  removed  by  one 
filtering,  filter  the  solutions  again. 

3.  The  color  can  also  be  removed  from  solutions  by 
putting  some  bone-black  into  them  and  boiling  for  a 
time.     Try  this  with  100-200  cc.  each  of  the  litmus 
and  indigo  solutions  used  in  the  first  part  of  the  ex- 
periment.    Use  1-2  grams  bone-black  in  each   case. 
Shake  the  solutions  frequently  while  heating.     Instead 
of  waiting  for  the  bone-black  to  settle,  the  solutions 
may  be  rendered  clear  by  filtering  through  an  ordi- 
nary filter-paper.     It  will  be  found  that  the  color  has 
been  removed  by  the  bone-black. 

*  Prepared  by  treating  1-2  grams  of  powdered  indigo  for  some 
time  with  4-5  cubic  centimetres  of  warm  concentrated  sulphuric  acid 
and  diluting  with  a  litre  of  water. 


DIRECT  UNION  OF  CARBON  AND    OXYGEN.       83 


DIEEOT  UNION  OF   CAKBON  AND   OXYGEN. 

k. 

EXPERIMENT  88. 

Apparatus  shown  in  Fig.  36  ;  oxygen  ;  concentrated  sulphuric  acid  ; 
calcium  chloride  ;  lime-water  ;  charcoal. 

1.  Arrange  an  apparatus  as  shown  in  Fig.  36.  A 
is  a  large  bottle  containing  oxygen.*  B  contains  con- 
centrated sulphuric  acid ;  a  U-tube  f  may  be  substi- 


FIG.  36. 

tuted  for  the  cylinder  if  it  be  desired.  C  contains  cal- 
cium chloride.  D  is  a  hard-glass  tube  containing  a 
small  piece  of  charcoal.  E  contains  clear  lime-water. 
(A  rather  better  arrangement  than  that  shown  in  the 
cut  is  to  substitute  for  the  funnel-tube  a  simple  piece 
of  glass  tubing  reaching  to  the  bottom  of  the  vessel 
and  connected  with  the  water-tap  ;  in  this  way  the 
flow  of  the  gas  can  be  precisely  regulated.  To  fill 
such  a  bottle  with  oxygen,  first  fill  it  with  water  ;  then, 

*  Do  not  attempt  to  connect  B  directly  to  an  oxygen-generator, 
I  See  Experiment  31 , 


84         DECOMPOSITION  OF  OXIDES  BY  CARBON 

EXPERIMENT  88— Continued. 

when  the  air  has  been  displaced  from  the  retort  and 
pure  oxygen  is  being  evolved,  connect  the  retort  with 
the  short,  bent  delivery-tube  and  allow  the  oxygen  to 
enter  the  bottle.  The  long  tube  is  meantime  con- 
nected with  another  tube  which  serves  as  a  siphon 
and  withdraws  the  water  as  fast  as  the  gas  is  passed 
in.) 

2.  When  the  apparatus  is  ready,  start  a  current  of 
gas  from  A  through  D.  Does  it  produce  any  effect 
in  El  Next  heat  D  until  the  charcoal  begins  to  glow. 
What  effect  is  now  produced  in  E?  To  what  is  this 
due  ?  Will  any  other  common  gas  produce  this  result 
with  lime-water? 

DECOMPOSITION   OF   OXIDES   BY   CARBON. 
EXPERIMENT  89. 

Powdered  copper  oxide  ;  powdered  charcoal  ;  arsenic-tube  ;  rubber- 
tubing  ;  lime-water  ;  concentrated  nitric  acid. 

1.  Mix  together  1-2  grams  powdered  copper  oxide, 
CuO,  and  about  one  tenth  its  weight   of   powdered 
charcoal ;  heat  in  an  arsenic  tube  to  which  i§  fitted 
an  outlet  tube.*     Pass  the  gas  which  is  given  off  into 
clear  lime-water  contained  in  a  test-tube. 

Is  it  carbon  dioxide  ? 

What  evidence  have  you  that  oxygen  has  been  ex- 
tracted from  the  copper  oxide  ?  What  is  the  appear- 
ance of  the  substance  left  in  the  tube  ?  Does  it  sug- 
gest the  metal  copper  ? 

2.  Treat  a  little  with  concentrated  nitric  acid  in  a 
test-tube. 


Compare  apparatus  ijsed  in  Experiment  Joa, 


CARBON  DIOXIDE, 


85 


EXPERIMENT  89 — Continued. 

What  should  take  place  if  the  substance  is  metallic 
copper  ?  (See  Experiment  79.) 

What  does  take  place  ? 

What  is  the  reaction  which  takes  place  between  the 
copper  oxide  and  the  charcoal  ?  Write  the  equation. 

Compare  the  action  of  hydrogen  with  that  of  carbon 
on  copper  oxide.  (See  Experiment  46.)  In  what  re- 
spects are  they  alike,  and  in  what  respects  do  they  differ? 

DECOMPOSTION   OF   OXIDES  BY   CARBON. 
EXPERIMENT  90. 

Same  apparatus  as  in   Experiment   89 ;    white  arsenic ;    powdered 
charcoal ;   lime-water. 

Mix  together  1-2  grams  of  white  arsenic,  As2O3, 
with  an  equal  weight  of  powdered  charcoal.  Fill  the 
bulb  of  a  dry,  clean  arsenic-tube  nearly  full  of  this 
mixture.  Clean  the  bore  of  the  tube  above  the  bulb 
and  then  attach  the  delivery-tube.  Heat  the  bulb  and 

pass  the  gas  given  off  through 
clear  lime-water.  What  is 
the  gas  ?  What  is  deposited 
in  the  bore  of  the  tube? 
How  does  it  differ  in  its  be- 
havior from  copper  ? 


CAKBON   DIOXIDE. 
EXPERIMENT  91. 

Test-tube  ;   glass  tube  ;  lime-water. 
Blow  through  some  clear 

lime-water  by  means  of   an   apparatus   arranged   as 
shown  in  Fig.  37, 


86  CAEBGN  DIOXIDE. 

EXPERIMENT  9 1 — Continued. 

What  evidence  have  you  that  your  lungs  give  off 
carbon  dioxide  ?  What  is  formed  ?  Add  a  few  drops 
of  dilute  hydrochloric  acid  ;  what  takes  place  ? 

EXPERIMENT  92. 

Test-tubes  ;  sodium  carbonate  ;  dilute  hydrochloric,  sulphuric,  nitric, 
and  acetic  acids. 

1.  Put  about  a  gram  of  sodium  carbonate  in  each  of 
four  test-tubes  ;  and  then  add  to  one  tube  about  4-5 
cubic    centimeters  of   dilute  hydrochloric  acid,  to    a 
second  the  same  quantity  of  dilute  sulphuric  acid, 
to  a  third  the  same  quantity  of  dilute  nitric  acid,  and 
to   the   fourth   the    same   quantity   of    dilute    acetic 
acid. 

What  takes  place  ?  Insert  a  burning  stick  into  the 
mouth  of  each  tube ;  what  takes  place  ? 

2.  Pass  the  gas  through  lime-water.     Is  it  carbon 
dioxide  ? 

3.  Perform  the  same  experiment  with  small  pieces 
of  marble.     What  gas  is  given  off? 

What  .conclusions  can  you  draw  from  these  obser- 
vations ? 

How  can  you  easily  detect  carbon  dioxide? 

EXPERIMENT  93. 

Apparatus  shown  in  Fig.  38  ;  marble  ;  ordinary  concentrated  hydro- 
chloric acid  ;  cylinders  ;  candle  on  wire  ;  scales. 

1.  Arrange  an  apparatus  as  shown  in  Fig.  38.  In 
the  flask  put  some  pieces  of  marble  or  limestone, 
and  pour  concentrated  hydrochloric  acid  on  it  to 
the  depth  of  about  an  inch.  Collect  the  gas  by  dis- 
placement of  air,  the  vessel  being  placed  with 


FORMATION  OF  CARBONATES. 


EXPERIMENT  93—  Continued. 

the  mouth  upward  since  tlie  gas  is  mucli  heavier  than 
air.     Fill  five  or  six  cylinders  or  bottles  with  the  gas. 

2.  Into     one     introduce     a 
lighted  candle,  and  afterwards 
a  burning  stick. 

What  takes  place  ? 

3.  With  another  proceed  as 
if  pouring  water  from  it.    Pour 
the   invisible    gas    upon    the 
flame  of  a  burning  candle. 

4.  Pour    some   of    the    gas 
from   one    vessel   to   another, 
and   show   that    it   has   been 
transferred. 

5.  Balance    a   beaker   on  a 
good-sized   scales,    and    pour 
carbon  dioxide  into  it. 

Explain  all  that  you  have  done,  giving  an  account 
of  the  properties  of  carbon  dioxide  as  'yon  have  ob- 
served them  in  the  above  experiments.  What  con- 
clusions are  you  justified  in  drawing  with  regard  to 
the  nature  of  the  gas  ? 

FORMATION   OF   CARBONATES. 
EXPERIMENT  94. 

Apparatus  for  making  carbon  dioxide  as  in  last  experiment  ;  caustic 
potash  ;  any  dilute  acid  ;  test-tube. 

Pass  carbon  dioxide  into  a  solution  of  caustic 
potash  (potassium  hydroxide  or  potassium  hydrate) 
until  it  will  absorb  no  more.  To  a  few  cc.  of  the 
solution  thus  obtained,  in  a  test-tube,  add  a  little  of 
any  dilute  acid. 


FIG.  38. 


88  CARBON  MONOXIDE. 

EXPERIMENT  94— Continued. 

What  gas  is  given  off  when  the  acid  is  added  ?  How 
do  you  know  ? 

Write  the  equations  expressing  the  reactions  which 
take  place  on  passing  the  carbon  dioxide  into  the 
caustic-potash  solution,  and  on  adding  an  acid  to  the 
solution. 

EXPERIMENT  95. 

Apparatus  for  carbon  dioxide  ;  lime-water;  filter  ;  dilute  acid. 

Pass  carbon  dioxide  into  50  to  100  cc.  clear  linie- 
water.  Filter  off  the  white  insoluble  substance.  Try 
the  action  of  a  little  dilute  acid  on  it. 

What  evidence  have  you  that  it  is  calcium  car- 
bonate ? 

How  could  you  easily  distinguish  between  lime- 
water  and  a  solution  of  caustic  potash  ? 

SOLUTION   OF   CALCIUM   CARBONATE. 
EXPERIMENT  96. 

Apparatus  for  carbon  dioxide  ;  lime-water. 
Pass  carbon  dioxide  first  through  a  little  water  to 
wash  it,  and  then  into  50-100  cc.  clear  dilute  lime- 
water,  until  the  precipitate  first  formed  redissolves. 
If,  after  the  gas  has  been  passed  for  some  time,  the 
solution  remains  cloudy,  filter  it.  Heat  the  clear 
solution  :  what  takes  place  ?  Why  ? 

CARBON  MONOXIDE. 
EXPERIMENT  97. 

Flask  of  200-250  cc.  capacity  ;  crystallized  oxalic  acid  ;  concentrated 
sulphuric  acid  ;  two  Wolff's  flasks  ;  solution  of  caustic  soda  ; 
cylinders  ;  bottle  for  collecting  gas. 

1.  Put  10  grams  crystallized  oxalic  acid  and  50-60 


CARBON  MONOXIDE  AS  A  REDUCING  AGENT.    89 

EXPEEIMENT  97—  Continued. 

grams  concentrated  sulphuric  acid  in  a  flask  of  appro- 
priate size.  Connect  with  two  Wolff's  flasks  contain- 
ing caustic  soda  solution  in  sucli  a  way  that  the  gas 
may  bubble  successively  through  the  two  solutions. 
Heat  the  contents  of  the  flask  gently.  Allow  the  air 
to  escape  *  and  then  collect  some  of  the  gas  in  cylin- 
ders over  water.  Next  connect  the  delivery-tube  with 
a  large  bottle  such  as  was  used  to  hold  oxygen  in 
Experiment  88 ;  collect  the  gas  so  long  as  it  is  given 
off.  Use  the  carbon  monoxide  thus  secured  in  Ex- 
periment 98. 

2.  Kemove,  one  by  one,  the  cylinders  from  the 
trough  and  light  the  gas.  What  is  the  color  of  the 
flame? 


CARBON  MONOXIDE   AS  A   REDUCING  AGENT. 
EXPERIMENT  98. 

Hard-glass  tube  ;  copper  oxide  ;  cylinder  ;  lime-water  ;  carbon  mon- 
oxide prepared  iu  last  experiment. 

Arrange  an  apparatus  as  described  in  Experiment 
88,  except  that  the  drying  apparatus  (B  and  6y,  Eig. 
36)  may  be  omitted.  In  the  tube  D  place  a  layer  of 
copper  oxide.  E  contains  lime-water.  A  current  of 
carbon  monoxide  is  now  passed  from  the  reservoir 
through  D  and  E.  Is  it  free  from  carbon  dioxide  ? 
Now  heat  D.  Is  carbon  dioxide  formed  ?  Is  the 
copper  oxide  reduced  ?  How  do  you  know  ? 

*  On  account  of  its  poisonous  character,  care  should  be  taken  that 
no  carbon  monoxide  escape  into  the  room,  if  it  can  be  avoided. 


90 


FLAME. 


OXYGEN   BURNING   IN  AN  ATMOSPHERE   OF 

HYDROGEN. 

EXPERIMENT  99. 

Bottle  filled  with  oxygen  ;  tip  for  burning  gas  ;  glass  tubing  shown 

in  Fig.  39. 

Into  one  end  of  a  piece  of  wide  glass  tubing  fit  a 
cork  through  which  passes  a  short  glass  tube  con- 
nected with  the  gas  supply.  A  retort-neck  will  serve 
as  well  as  anything  for  the  wide  tube,  as  is  shown  in 
Fig.  39.  Fill  a  bottle  with  oxygen,  as  in  Experiment 


FIG.  39. 

88 ;  connect  with  the  water-tap,  and  arrange  the  ap- 
paratus so  that  a  stream  of  oxygen  is  forced  through 
a  small  tip.  Now  turn  on  the  illuminating-gas  and 
light  it  at  the  mouth  of  the  wide  tube.  Insert  the  jet 
of  oxygen  into  the  wide  tube,  as  shown  in  the  figure. 
Does  the  oxygen  burn  in  the  atmosphere  of  illuminat- 
ing-gas ? 

FLAME. 

EXPERIMENT  100. 

Wire  gauze  ;  Bunsen  burner. 

1.  Light  a  Bunsen  burner.     Bring  down  upon  the 


REDUCTION  WITH  THE  AID  OF  THE  BLOWPIPE.   91 

EXPERIMENT  100—  Continued. 

flame  a  piece  of  rather  fine  brass-  or  iron-wire  gauze. 
Does  the  flame  pass  through  the.  gauze  ? 

Apply  a  light  above  the  gauze  and  above  the  out- 
let of  the  burner.  Is  there  any  gas  unburned  above 
the  gauze  ?  Why  does  the  flame  not  pass  through  the 
gauze  ? 

2.  Turn  on  a  Bunsen  burner.  Do  not  light  the  gas. 
Hold  a  piece  of  wire  gauze  about  one  and  a  half  to 
two  inches  above  the  outlet.  Apply  a  lighted  match 
above  the  gauze.  Where  is  the  flame  ? 

What  is  below  the  gauze  ?     Prove  it. 

What  is  the  principle  upon  which  the  Davy  safety- 
lamp  is  constructed  ?  For  what  is  it  used  ? 

REDUCTION  WITH   THE  AID  OP   THE  BLOW- 
PIPE. 

EXPERIMENT  101. 

Stick  of  charcoal ;  blowpipe;  lead  oxide;  dry  sodium  carbonate. 

Select  a  piece  of  charcoal  about  4  inches  long  by  1 
inch  wide  and  ^—1  inch  thick,  with  one  surface  plane.* 
Near  the  end  of  the  plane  surface  make  a  cavity  by 
pressing  the  edge  of  a  small  coin  against  it,  and  turn- 
ing it  completely  round  a  few  times.  Mix  together 
small  equal  quantities  of  dry  sodium  carbonate  and 
lead  oxide.  Put  a  little  of  the  mixture  in  the  cavity 
in  the  charcoal  and  heat  it  in  the  reducing  flame  pro- 
duced by  the  blowpipe.  The  sodium  carbonate  melts 
but  is  not  otherwise  changed:  its  use  is  simply  that 
of  a  "  flux."  In  a  short  time  globules  of  metallic  lead 

*  Charcoal  specially  prepared  for  blowpipe- work  may  be  had  of 
dealers. 


92   OXIDATION  WITH  THE  AID  OF  THE  BLOWPIPE. 

EXPERIMENT  101— Continued. 

will  be  seen  in  the  molten  mass.  After  cooling,  scrape 
the  solidified  substance  out  of  the  cavity  in  the  char- 
coal. Put  it  into  a  small  mortar,  treat  it  with  a  little 
water,  and,  after  breaking  it  up  and  allowing  as  much 
as  possible  to  dissolve,  pick  out  the  metallic  beads. 
Are  they  malleable  or  brittle?  Is  metallic  lead  mal 
leable  or  brittle  ?  Are  they  dissolved  in  hydrochloric 
acid?  Is  lead  soluble  in  hydrochloric  acid?  Are 
they  soluble  in  nitric  acid  ?  Is  lead  soluble  in  nitric 
acid  ?  The  action  of  the  acids  may  be  tried  by  put- 
ting the  bead  on  a  small  dry  watch-glass  and  adding 
a  few  drops  of  acid.  Does  the  substance  act  like  lead? 
What  has  become  of  the  oxygen  with  which  the  lead 
was  combined  in  the  oxide  ?  Is  there  any  special 
advantage  in  having  a  support  of  charcoal  for  this 
experiment  ? 

OXIDATION  WITH  THE  AID  OF  THE  BLOWPIPE. 
EXPERIMENT  102. 

Charcoal  as  before;  blowpipe;  bit  of  lead. 

Heat  a  small  piece  of  metallic  lead  on  charcoal  in 
the  oxidizing  flame  of  the  blowpipe.  Notice  the  for- 
mation of  the  oxide,  which  forms  a  yellow  coating  or 
film  on  the  charcoal  in  the  neighborhood  of  the  metal. 
Is  it  easier  to  reduce  lead  oxide  or  to  oxidize  lead,  on 
charcoal?  Why? 

Is  there  any  analogy  between  the  process  of  oxidiz- 
ing lead  and  the  burning  of  hydrogen  ?  In  what  does 
the  analogy  consist?  What  differences  are  there  be- 
tween the  two  processes  ? 


BROMINE.  93 

BROMINE. 
EXPERIMENT  103. 

Apparatus  shown  in  Fig.  19;  potassium  bromide;  manganese  dioxide; 
concentrated  sulphuric  acid. 

1.  Mix  together  3.5  grams  potassium  bromide  and  7 
grams  manganese  dioxide.     Put  the  mixture  into  a 
500-cc.  flask ;  connect  with  a  condenser  (see  Fig.  19, 
Experiment  49).     Set  up  the  apparatus  under  a  hood. 
Pour  15  cc.  concentrated  sulphuric  acid  into  90  cc. 
water,  mix  and,  after  the  liquid  is  cool,  pour  it  upon 
the  mixture  in  the  flask.     Heat  gently,  when  bromine 
will  be  given  off  in  the  form  of  vapor  ;  a  part  of  this 
will  condense  and  collect  in  the  receiver.    It  is  a  good 
thing  to  put  a  few  cc.  of  water  in  the  receiver :  the 
bromine  will  sink  below  this  and  will  thus  be  some- 
what  protected   against   evaporation.     The  receiver, 
too,  should  fit  close  to  the  condenser-tube  and  should 
be  kept  cool  with  running  water.    If  these  precautions 
are  taken  there  is  little  danger  of  bromine  escaping  in 
sufficient  quantity  to  do  any  harm. 

2.  What  is  the  nature  of  bromine  ?     Is  it  soluble  in 
water  ?     Write  the  reaction  showing  its  formation  :  it 
is  similar  to  that  which  shows  the  isolation  of  chlo- 
rine.    What  action  does  sulphuric  acid  have  on  man- 
ganese dioxide  ?     W^rite  the  equation.     What  action 
does  the  acid  have  on  potassium  bromide  ?    Write  the 
equation.     WThat  would  be  the  products  if  the  two  ac- 
tions took  place  together  ?    Would  a  current  of  oxygen 
gas  passed  through  hydrobromic  acid  produce  bro- 
mine ?     Why  ? 

3.  If  the  formula  of  manganese  sulphate  is  MnSO4 , 
what  is  the  valence  of  manganese  ?     What  would  you 


94  IODINE  AND  HYDRIODIC  ACID. 

EXPERIMENT  103— Continued. 

expect  the  formula  of  manganese  chloride  to  be ;  of 
manganese  oxide  ?  What  is  the  formula  of  manganese 
dioxide  ?  Is  the  valence  of  manganese  greater  toward 
oxygen  or  toward  chlorine  ? 

BROMINE  AND   HYDROBROMIC   ACID. 
EXPERIMENT  104, 

Evaporating- dish;  potassium  bromide;  concentrated  sulphuric  acid; 
potassium  or  sodium  chloride. 

1.  In  a  small  porcelain  evapora ting-dish   under  a 
hood  put  two  or  three  small  crystals  of  potassium 
bromide.     Pour  on  them  a  few  drops  of  concentrated 
sulphuric  acid. 

What  do  you  see  ?  What  color  have  the  fumes  ?  To 
what  is  this  color  due  ? 

2.  Treat  two  or  three  crystals  of  potassium  chloride 
or  sodium  chloride  in  the  same  way. 

What  difference  is  there  between  the  two  cases  ? 
Explain  the  difference. 

IODINE  AND   HYDRIODIC   ACID. 
EXPERIMENT  105. 

Large  flask;  potassium  iodide;  manganese  dioxide;  concentrated  sul- 
phuric acid. 

Mix  about  2  grams  potassium  iodide  with  about 
twice  its  weight  of  manganese  dioxide.  Treat  with  a 
little  concentrated  sulphuric  acid  in  a  large  flask.  Heat 
gently  on  a  sand-bath. 

What  takes  place  ?     What  is  the  color  due  to  ? 

Lay  some  folds  of  wet  filter-paper-on  the  upper  part 
of  the  flask  :  the  iodine  will  be  deposited  on  the  cooled 
glass  in  grayish-black  crystals.  If  possible,  collect 
these  and  use  them  in  the  next  Experiment. 


IODINE  AND  STAR'CH.  9£ 

SOLVENTS  FOR  IODINE. 
EXPERIMENT  106. 

Iodine;  alcohol;  potassium  iodide;  test-tubes. 

Make  solutions  of  iodine  in  water,  in  alcohol,  and  in 
a  water  solution  of  potassium  iodide.  In  each  case 
use  one  or  two  small  crystals  of  iodine  and  a  small 
test-tube.  For  the  solution  of  potassium  iodide  dis- 
solve a  crystal  of  that  salt  the  size  of  a  pea  in  two«or 
three  cc.  of  water. 

Is  iodine  soluble  in  water ;  is  it  soluble  in  alcohol ; 
is  it  soluble  in  a  solution  of  potassium  iodide  ? 

Which  is  the  best  solvent  ? 

IODINE  AND   STARCH. 

EXPERIMENT  107. 

Evaporating-dish;  test-tubes;  starch;  iodine;  potassium  iodide;  chlo- 
rine-water, made  by  passing  chlorine  gas  into  water. 

1.  Make  some  starch-paste  by  covering  a  few  grains 
of  starch  in  a  porcelain  evaporating-dish  with    cold 
water,  grinding  this  to  a  paste,  and  pouring  200-300 
cc.  boiling-hot  water  on  it. 

2.  After  cooling  add  a  few  drops  of  this  paste  to  a 
water  solution  of  iodine. 

What  change  takes  place  ? 

3.  Now  add  a  little   of  the  paste  to  a  very  dilute 
water  solution  of  potassium  iodide,  prepared  as  in  Ex- 
periment 106. 

Is  there  any  change  of  color  ?  Add  a  drop  or  two 
of  a  dilute  solution  of  chlorine  in  water.  What  takes 
place  ? 

Explain  what  you  have  seen.     Why  does  the  addi- 


HYDROFLUORIC  ACID. 

EXPERIMENT  107—  Continued. 

tion  of  chlorine-water  produce  a  color  when  potassium 
iodide  alone  does  not  ? 

Does  chlorine-water  alone  form  a  blue  compound 
with  starch  ?  Try  it. 

IODINE   AND  HYDKIODIC  ACID. 
EXPERIMENT  108. 

Test-tubes;  potassium  iodide;  concentrated  sulphuric  acid. 

Treat  a  few  small  crystals  of  potassium  iodide  with 
concentrated  sulphuric  acid.  What  do  you  notice  ? 

Compare  with  the  results  obtained  when  potassium 
bromide  and  sodium  chloride  were  treated  in  a  similar 
way 

HYDROFLUORIC  ACID. 
EXPERIMENT  109. 

Lead  or  platinum  crucible  ;  powdered  fluor-spar  ;  concentrated  sul- 
phuric acid  ;  wax  or  paraffin. 

In  a  lead  or  platinum  vessel  put  a  few  grams  (5-6) 
of  powdered  fluor-spar,  and  pour  on  it  enough  concen- 
trated sulphuric  acid  to  make  a  thick  paste.  Cover 
the  surface  of  a  piece  of  glass  with  a  thin  layer  of  wax 
or  paraffin,  and  through  this  scratch  some  letters  or 
figures,  so  as  to  leave  the  glass  exposed  where  the 
scratches  are  made.  Put  the  glass  with  the  waxed 
side  downward  over  the  vessel  containing  the  fluor- 
spar, and  let  it  stand  for  some  hours.  Take  off  the 
glass,  scrape  off  the  coating,  and  the  figures  which 
were  marked  through  the  wax  or  paraffin  will  be  found 
etched  on  the  glass. 

What  chemical  changes  have  taken  place  in  this  ex- 
periment ?  Write  the  equations. 


SULPHUR  IN  MONOCLINIC  CRYSTALS.  97 

DISTILLATION   OF   SULPHITE. 
EXPERIMENT  110. 

Retort  ;  beaker  ;  sulphur. 

In  a  dry  retort  of  75-100  cc.  capacity  and  provided 
with,  a  rather  wide  neck,  put  20-30  grams  roll-sulphur 
and  heat.  Observe  the  changes  which  take  place  as 
the  temperature  rises.  Does  the  sulphur  boil  ?  Place 
a  dish  of  cold  water  below  the  outlet  and,  if  necessary, 
heat  the  neck  of  the  retort  from  time  to  time  to  pre- 
vent the  sulphur's  solidifying  as  it  flows  down.  Al- 
low the  molten  sulphur  to  flow  into  the  .water.  Note 
the  changes  in  color.  Examine  the  amorphous  sul- 
phur :  is  it  translucent  or  opaque ;  is  it  brittle  or 
elastic  ? 

SULPHUR  IN  MONOCLINIC   CRYSTALS. 

EXPEEIMENT   111. 
Porcelain  or  clay  crucible  ;  sulphur. 

1.  In  a  covered  porcelain  or  clay  crucible  carefully 
melt  a  few  grams  of  roll-sulphur.     Let  it  cool  slowly 
and  when  a  thin  crust  has  formed   on   the   surface 
make  a  hole  through  this  and  pour  out  the  liquid  part 
of  the  sulphur.     The  inside  of  the  crucible  will  be 
found  lined  with  honey-yellow  needles  which  belong 
to  the  monoclinic  system. 

2.  Take  out  a  few  of  the  crystals  and  examine  them. 
Are   they  brittle  or  elastic?     What   is   their  color? 
Are  they  opaque,  transparent  or  translucent  ? 

3.  Lay  the  crucible  aside,  and  in  the  course  of  a 
few  days  again  examine  the  crystals.     What  changes, 
if  any,  have  taken  place  ? 


98        COMBINATION  OF  SULPHUR   WITH  METALS. 

SULPHUR  IN  ORTHORHOMBIC   CRYSTALS. 
EXPERIMENT  112. 

Evaporating-disli ;  roll-sulphur  ;  carbon  disulpliide. 

Dissolve  2-3  grams  roll-sulphur  in  5-10  cc.  carbon 
disulphide.*  Put  the  solution  in  a  shallow  vessel, 
and  allow  the  carbon  disulphide  to  evaporate  by  stand- 
ing in  the  air. 

What  is  the  appearance  of  the  crystals?  Are  they 
dark  yellow  or  bright  yellow  ? 

Are  they  brittle  or  elastic  ? 

State  in  tabular  form  the  properties  of  the  two  allo- 
tropic  forms  of  sulphur. 

COMBINATION  OF   SULPHUR  WITH   METALS. 
EXPERIMENT  113. 

Wide  test-tube  ;  sulphur  ;  copper-foil. 

In  a  wide  test-tube  heat  some  sulphur  to  boiling. 
Introduce  into  it  small  pieces  of  copper-foil  or  sheet- 
copper,  or  better,  hold  a  narrow  piece  of  thin  sheet- 
copper  so  that  the  end  just  dips  into  the  boiling  sul- 
phur. 

What  evidence  have  you  that  action  takes  place  ? 
(Compare  Experiment  10.) 

Compare  the  chemical  action  in  this  case  with  that 
which  takes  place  when  copper-foil  is  put  into 
chlorine. 

*  See  foot-note,  Experiment  9. 


HYDROGEN  SULPHIDE. 


99 


HYDROGEN  SULPHIDE   (SULPHURETTED 
HYDROGEN). 

EXPEEIMENT   114. 

Apparatus  ?s  shown  in  Fig.  40  ;  iron  sulphide  ;  concentrated  hydro- 
chloric acid  ;  cylinders  or  bottles. 

1.  Under  a  hood  arrange  an  apparatus  as  shown  in 
Fig.  40.     Put  a  small  handful  of  sulphide  of  iron,  FeS, 
in  the  flask,  and  pour  upon  it  hydrochloric  acid  pre- 
pared by  mixing  equal  volumes  of  the  ordinary  con- 
centrated acid  and  water. 

2.  Pass  the  gas  through  a  little  water  contained  in 


the   wash-cylinder   A.      Pass   some   of   the   gas   into 
water. 

Is  the  gas  soluble  in  water  ? 

3.  Collect  some  of  the  gas  by  displacement  of  air  as 
in  the  case  of  chlorine  and  hydrochloric  acid.     The 
specific  gravity  of  hydrogen  sulphide  is  1.178. 

4.  Set  fire  to  some  of  the  gas  contained  in  a  cylin- 
der. 


100  SULPHIDES  INSOLUBLE  IN  WATER. 

EXPERIMENT  111— Continued. 

What  products  are  formed  in  case  both  sulphur  and 
hydrogen  burn  ? 

5.  Hydrochloric  acid,  water,  ammonia,  marsh-gas, 
and  hydrogen  sulphide  are  all  compounds  of  hydro- 
gen. Compare  them  with  special  reference  to  their 
conduct  towards  oxygen. 

SULPHIDES  INSOLUBLE  IN  WATEE. 
EXPERIMENT  115. 

Apparatus  for  making  hydrogen  sulphide  as  in  last  experiment ;  test- 
tubes  ;  lead  nitrate ;  zinc  sulphate  ;  arsenic  trioxide ;  dilute 
hydrochloric  acid. 

Prepare  a  dilute  solution  of  lead  nitrate  by  dissolv- 
ing about  a  gram  in  8-10  cc.  water  in  a  test-tube  ;  a 
solution  of  zinc  sulphate  of  the  same  strength  ;  and  a 
solution  of  arsenic  by  boiling  about  a  gram  of  arsenic 
trioxide  ("  white  arsenic "  or  arsenious  acid)  with 
8-10  cc.  dilute  hydrochloric  acid  in  a  test-tube.  Pass 
hydrogen  sulphide*  through  each  solution,  taking  care 
to  wash  the  delivery-tube  each  time  before  inserting 
it  into  a  fresh  solution. 

What  do  you  observe  in  each  case  ?  The  hydrogen 
of  the  hydrogen  sulphide  has  in  each  case  been  re- 
placed by  a  metallic  element.  The  sulphides  of  lead, 
zinc,  and  arsenic  have  been  formed,  and,  being  insolu- 
ble in  water,  have  been  precipitated.  What  are  their 
respective  colors?  Treat  each  with  dilute  hydro- 
chloric acid  :  what  result  is  produced  in  each  case  ? 

*  The  apparatus  for  generating  hydrogen  sulphide  should  always 
be  set  up  under  a  hood  or  in  some  room  other  than  the  working  lab- 
oratory. 


SULPHUR  DIOXIDE.  101 


SULPHUE  DIOXIDE. 
EXPERIMENT  116. 

Flask  ;  sheet-copper  or  turnings  ;  concentrated  sulphuric  acid  ;  cyl- 
inder or  bottle  ;  candle  or  splinter. 

1.  Put  eight  or  ten  pieces  of  sheet-copper,  one  to 
two  inches  long,  and  about  half  an  inch  wide,  or  else 
10—20  grams  copper  turnings,  into  a  500-cc.  flask  pro- 
vided with  a  cork  and  delivery-tube ;  place  it  under 
the  hood  and  pour  15  to  20  cc.  concentrated  sulphuric 
acid  into  it.     Heat  gently.     The  moment  the  gas  be- 
gins to  come  off,  lower  the  flame,  and  keep  it  at  such 
a  height  that  the  evolution  is  regular  and  not  too  ac- 
tive. 

2.  Pass  some  of  the  gas  into  a  bottle   containing 
water.     Is  it  soluble  in  water  ? 

3.  Collect  a  vessel  full  by  displacement  of  air.     (It 
is  more  than  twice  as  heavy  as  air,  its  specific  gravity 
being  2.24.) 

4.  See  whether  the  gas  will  burn  or  support  com- 
bustion. 

Is  the  gas  colored?  Is  it  transparent?  Has  it  any 
odor? 

In  what  experiment  already  performed  was  this  gas 
formed  ? 

SULPHUE  DIOXIDE  AS  A  BLEACHING  AGENT. 
EXPERIMENT  117. 

Porcelain  crucible  ;  bell-iar  or  wide-mouthed  bottle  ;    tripod ;  sul- 
phur ;  colored  flowers. 

Under  a  hood  burn  a  little  sulphur  in  a  porcelain 
crucible  under  a  bell-jar.  Place  over  the  crucible  on  a 


102  PHOSPHOR  U^PHOSPHINE. 

EXPERIMENT  117—  Continued. 

tripod  some  flowers.     "What  change  takes  place  in  the 
flowers  ? 

Compare  the  action  with  the  action  of  chlorine. 
Does  sulphur  dioxide  act  in  the  same  way  that  chlo- 
rine does  ? 

CHEMICAL  ACTIVITY   OF  PHOSPHORUS. 
EXPERIMENT  118. 

Porcelain  crucible  or  evaporatiug-dish  ;  phosphorus  ;  iodine. 

Under  a  hood  bring  together  in  a  porcelain  crucible 
or  evaporating-dish  a  piece  of  phosphorus  about  the 
size  of  a  pea  and  about  the  same  quantity  of  iodine. 
What  takes  place?  What  is  the  cause  of  the  light 
and  heat? 

It  will  be  seen  that  simple  contact  is  sufficient  to 
enable  the  two  substances  to  act  upon  one  another 
Compare  the  action  of  phosphorus  towards  iodine  with 
its  action  towards  oxygen. 

What  other  examples  have  you  had  of  the  direct 
combination  of  two  elements  by  simple  contact  ? 

What  examples  have  you  had  of  direct  combination 
of  two  elements  at  elevated  temperatures  ? 

PHOSPHINE. 
EXPERIMENT  119. 

Apparatus  shown  in  Fig.  41 ;   zinc ;   dilute  sulphuric  acid  ,  oaustic 
potash  ;  phosphorus  ;  cylinder  ;  trough  or  dish. 

1.  Under  a  hood  arrange  an  apparatus  as  shown  in 
Fig.  41.  In  the  flask  B,  which  should  not  be  larger 
than  the  100-cc.  or  125-cc.  size,  put  about  5  grams 
caustic  potash  dissolved  in  10-15  cc.  water  and,  after 


PHOSPHINE. 


103 


EXPERIMENT  119—  Continued. 

the*  solution  has  become  quite  cold,  add  a  few  small  pieces 
of  phosphorus  the  size  of  a  pea,  and  push  the  stopper 
in  tight.  Pass  hydrogen  free  from  air  through  the 
apparatus  from  the  generating-flask  A  until  all  the 
air  is  displaced;  then  disconnect  fit  D,  leaving  the 
rubber  tube,  closed  by  the  pinch-cock,  on  the  tube 
which  enters  the  small  flask.  Gently  heat  the  coii- 


FIG.  41. 


tents  of  the  flask,  Avhen  gradually  a  gas  will  be  evolved 
and  will  escape,  mixed  at  first  with  hydrogen,  through 
the  water  in  C.  As  each  bubble  comes  in  contact 
with  the  air  it  takes  fire  and  the  products  of  combus- 
tion arrange  themselves  in  rings  which  become  larger 
as  they  rise.  They  are  extremely  beautiful,  particu- 
larly if  the  air  of  the  room  is  quiet.  Both  the  phos- 
phorus and  the  hydrogen  combine  with  oxygen  in 
the  act  of  burning. 

2.  After  a  little  of  the  gas  has  been  allowed  to  es- 
cape, collect  some  in  a  cylinder  over  water.     Let  it 


104: 


AESINE. 


EXPEEIMENT  119—  Continued. 

stand  some  time  in  contact  with  the  water  in  the 
lower  part  of  the  cylinder,  and  then  turn  it  mouth  up 
while  covered  with  a  glass  plate.  Remove  the  plate  : 
does  the  gas  take  fire  as  it  did  at  first  ?  Why  ? 

ARSINE. 
EXPERIMENT  120. 

Apparatus  shown  in  Fig.  42  ;  granulated  zinc  ;  dilute  sulphuric  acid  ; 
granulated  calcium  chloride  ;  arsenic  trioxide  ;  dilute  hydro- 
chloric acid. 

Arrange  an  apparatus  as  shown  in  Fig.  42.  The 
U-tube  contains  granulated  calcium  chloride  for  the 
purpose  of  drying  the  gases.  The  Bunsen  burner  is 


FIG.  42. 

not  to  be  lighted  in  this  experiment.  The  apparatus 
should  stand  under  the  hood.  Put  some  granulated 
zinc  in  the  Wolff's  flask,  pour  dilute  sulphuric  acid 
on  it  and  connect  with  the  U-tube.  When  the  air  is 
all  out  of  the  vessel  and  the  hydrogen  is  lighted,  add 


ACTION  OF  CARBON  ON  ARSENIC  TRIOXIDE.    105 

EXPERIMENT  120 — Continued. 

slowly  a  little  of  a  solution  of  arsenic  trioxide,  As2O3 , 
in  hydrochloric  acid.  What  change  takes  place  in 
the  flame  ?  Is  the  color  changed  ?  Are  fumes  given 
off  ?  What  must  these  be  ?  What  other  product  of 
combustion  would  you  expect  to  be  formed?  (See 
Experiment  121.) 

ARSENIC  SPOTS. 
EXPERIMENT  121. 

Apparatus  used  in  last  experiment ;  piece  of  white  porcelain. 

1.  Into   the   flame    of   the    burning   hydrogen   and 
arsine  produced  in  the  last  experiment  introduce  a 
piece  of  porcelain,  as  the  bottom  of  a  small  porcelain 
dish  or  a  crucible,  and  notice  the  appearance  of  the 
spots. 

2.  Heat  by  means  of   a   Bunsen  burner  the  tube 
through  which  the  gas  is  passing,  which  should  be  of 
hard  glass  :  is  a  deposit  formed  on  the  glass  ?     What 
is  its  character  ?     To  what  is  it  due  ?     Will  passage 
through  a  hot  tube  decompose  ammonia  or  phosphine  ? 

ACTION   OF    CARBON   ON   ARSENIC   TRIOXIDE. 
EXPERIMENT  122. 

Arsenic  trioxide  ;  finely  powdered  charcoal  ;  ignition-tube. 

Mix  together  about  equal  small  quantities  of  arsenic 
trioxide  and  finely-powdered  charcoal.  Heat  the  mix- 
ture in  a  dry  arsenic-tube. 

What  change  takes  place?  (See  Experiment  90.) 
What  is  this  kind  of  action  called  ? 


106  ANTIMONY  SPOTS. 

ANTIMONY. 
EXPERIMENT  123. 

Charcoal ;  blowpipe  ;  antimony  ;  arsenic. 

1.  Under  a  hood  heat  a  small  piece  of  antimony 
on  charcoal  by  means  of  the  blowpipe.     Notice  the 
formation  of  the  white  coating  on  the  charcoal  around 
the  place  where  the  substance  burns.     Does  the  anti- 
mony melt  ? 

2.  Heat  a  small  piece  of  arsenic  in  the  same  way. 
Does  it  melt  ?     Does  it  form  a  deposit  ?     Have  the 
fumes  an  odor  ?    Which  is  more  volatile  ?     Could  you 
distinguish  arsenic  and   antimony  by  means  of   the 
blowpipe  ? 

STIBINE. 
EXPERIMENT  124. 

Apparatus  as  shown  in  Fig.  42 ;  tartar  emetic  ;  piece  of  white  porce- 
lain. 

Under  a  hood  make  some  stibine,  using  the  same 
kind  of  apparatus  as  that  for  making  arsine.  Instead 
of  a  solution  of  arsenic  use  a  solution  of  tartar  emetic 
in  dilute  hydrochloric  acid. 

What  differences,  if  any,  do  you  notice  between 
what  takes  place  in  this  case  and  what  you  saw  in 
Experiment  120  ? 

ANTIMONY  SPOTS. 

EXPERIMENT  125. 

Introduce  a  piece  of  porcelain  into  the  flame  and 
notice  the  deposit,  or  antimony  spot.  Compare  the 
spots  with  those  formed  with  arsenic:  is  there  any 
difference  in  the  appearance  ? 

Heat  the  porcelain  on  which  the  spots  are  and 
notice  whether  any  change  takes  place. 


CHLORIDES.  107 

BISMUTH. 
EXPERIMENT  126. 

Charcoal  ;  blowpipe  ;  bit  of  bismuth. 

Heat  a  small  piece  of  bismuth  on  charcoal  by 
means  of  the  blowpipe.  Compare  the  results  obtained 
with  antimony  and  with  arsenic,  as  regards  volatility, 
odor  of  oxide,  color  of  deposit,  etc.,  with  those  ob- 
tained with  bismuth. 

BORAX  AND  BORIC  ACID. 
EXPERIMENT  127. 

Beaker;  borax;  concentrated  sulphuric  acid;  evaporating-dish; 
alcohol. 

Make  a  hot  solution  of  30  grams  crystallized  borax 
in  120  cc.  water.  Add  slowly  10  grams  concentrated 
sulphuric  acid.  On  the  liquids'  cooling  the  boric  acid 
will  crystallize  out.  Compare  borax  and  boric  acid. 
Which  is  more  soluble  in  alcohol?  Shake  a  little  of 
each  with  alcohol  and  then  in  each  case  pour  the  al- 
cohol into  a  clean  evaporating-dish  and  set  fire  to  it. 
Do  the  flames  differ  ? 

CHLORIDES. 
EXPERIMENT  128. 

Test-tubes;  solutions  of  silver  nitrate,  sodium  chloride,  hydrochloric 
acid,  and  ammonia. 

Dissolve  a  small  crystal  of  silver  nitrate  in  pure 
water.  Add  to  a  small  quantity  of  this  solution  in  a 
test-tube  a  few  drops  of  dilute  hydrochloric  acid. 
What  is  the  precipitate  thus  formed  ?  To  another 
small  portion  of  the  solution  add  a  few  drops  of  a 
dilute  solution  of  common  salt,  or  sodium  chloride, 


108  HYDROXIDES, 

EXPERIMENT  128— Continued. 

NaCl.  The  white  substance  produced  iu  this  case  is 
also  silver  chloride.  Add  ammonia  to  each  tube ; 
does  the  precipitate  completely  dissolve  ?  If  not,  add 
more  ammonia.  Now  add  dilute  nitric  acid  to  each 
tube:  what  happens?  On  standing  exposed  to  the 
light  the  precipitates  change  color,  becoming  finally 
dark  violet. 

The  reactions  involved  are  these  :  Hydrochloric  acid 
and  sodium  chloride  each  precipitate  silver  chloride 
from  a  solution  of  silver  nitrate — 

AgNO,  +  HOI  =  AgCl  +  HNO3 ; 
AgN03  +  NaCl  =  AgCl  +  NaNO  - 

forming  at  the  same  time  nitric  acid  in  the  one  case, 
and  sodium  nitrate  in  the  other.  [Is  silver  chloride 
soluble  in  nitric  acid  ?]  Ammonia  forms  with  silver 
chloride  a  soluble  compound.  Nitric  acid  breaks 
down  this  compound,  forming  ammonium  nitrate  and 
free  silver  chloride ;  the  latter,  being  insoluble,  is 
again  precipitated. 

Silver  salts  are  decomposed  by  sunlight. 

HYDROXIDES. 
EXPERIMENT  129. 

Evaporating-disli;  lime. 

To  some  pieces  of  freshly  burned  lime  add  a  little 
cold  water.  Let  the  action  between  the  lime  and  the 
water  begin,  then  add  a  little  more  water.  Repeat 
this  until  the  lime  has  crumbled  to  a  dry  white  powder. 
The  equation 

CaO  +  H30  =  Ca(OH), 

represents  the  action.     The  process  is  called  slaking. 


SULPHIDES.  109 

EXPEEIMENT  129—  Continued. 

Is  heat  evolved  ?  Why  ?  How  can  you  show  that 
the  substance  obtained  is  not  calcium  oxide  ? 

EXPERIMENT  130. 

Test-tubes ;   magnesium  sulphate  ;   caustic  soda ;   dilute   sulphuric* 
hydrochloric,  and  nitric  acids. 

To  a  dilute  solution  of  magnesium  sulphate  add  a 
dilute  solution  of  caustic  soda  :  the  precipitate  is  mag- 
nesium hydroxide.  Is  it  soluble  in  sulphuric  acid  ? 
Why  would  you  expect  it  to  be  soluble  ?  Is  it  soluble 
in  hydrochloric  acid  ?  What  chlorides  are  insoluble 
in  water  ?  Is  it  soluble  in  nitric  acid  ?  Do  you  know 
of  any  nitrate  insoluble  in  water  ? 

EXPERIMENT  131. 

Test-tubes ;  ferric  chloride  ;  caustic  soda  ;  dilute  sulphuric,  hydro- 
chloric, and  nitric  acids. 

To  a  dilute  solution  of  that  chloride  of  iron  which  is 
called  ferric  chloride  add  caustic  soda  solution.  The 
reddish  precipitate  is  ferric  hydroxide.  Is  it  soluble 
in  each  of  the  three  acids  used  in  Experiment  130  ? 
Why  would  you  expect  it  to  be  soluble  ? 

SULPHIDES. 
EXPERIMENT  132. 

Test-tubes;  ammonium  sulphide;  a  copper  salt;  a  lead  salt;  an  iron 

salt. 

Add  ammonium  sulphide  successively  to  dilute  so- 
lutions of  a  copper  salt,  a  lead  salt,  and  an  iron  salt. 
Note  what  takes  place  in  each  case.  Is  there  any  dif- 
ference in  color  among  the  precipitates  ?  Treat  each 
in  turn  with  dilute  hydrochloric  acid  :  is  there  any 
difference  to  be  noted  among  them  ? 


110  NITRATES— SULPHATES. 

NITKATES. 
EXPERIMENT  133. 

Charcoal;  blowpipe;  potassium,  copper,  and  lead  nitrates. 

1.  Heat  2-3  grams  potassium  nitrate  on  charcoal 
with  the  blowpipe  flame.     The   decomposition  with 
evolution  of  gas  is  called  deflagration.     Does  the  salt 
contain  water  of  crystallization  ?     Heat  some  in  an 
arsenic-tube  :  is  water  given  off?     What  change  takes 
place  ?     (See  Experiment  80.) 

2.  Heat  some  crystallized  copper  nitrate  on  char- 
coal and  also  in  an  arsenic-tube  :  what  change  does  it 
undergo  ?     Is  water  given  off  ?     (See  Experiments  12 
and  79.) 

3.  Heat  some  poivdered  lead  nitrate  on  charcoal  and 
also  in  an  arsenic-tube  :  What  change  takes  place  ?   Is 
water  evolved  ?     (See  Experiment  80.) 

SULPHATES. 
EXPERIMENT  134. 

Beaker ;  water-bath  ;  iron  turnings  or  filings  ;  dilute  sulphuric  acid  ; 
test-tube. 

Under  a  hood  dissolve  some  iron  in  dilute  sulphuric 
acid :  what  is  given  off  ?  When  the  action  is  over, 
filter  the  solution  after  having  warmed  it,  and  set  it 
aside  to  crystallize.  If  after  standing  it  will  not 
crystallize,  evaporate  down  to  half  its  bulk  on  the 
water-bath,  and  again  set  it  aside  to  crystallize. 

What  is  the  appearance  of  the  salt  ?  Does  it  con- 
tain water  of  crystallization  ?  Heat  some  to  a  high 
temperature  in  an  arsenic-tube :  what  are  the  white 
fumes  evolved  ?  Ferrous  sulphate  is  also  called 
"  copperas  "  and  "  green  vitriol."  What  is  "  oil  of 
vitriol "  ?  Do  the  white  fumes  suggest  it  ? 


SULPHATES.  Ill 

EXPERIMENT  135. 

Beaker  ;  copper-foil  or  turnings  ;  concentrated  sulphuric  acid. 

Dissolve  soine  copper  in  Lot  concentrated  sulphuric 
acid ;  perform  this  part  of  the  experiment  under  a 
good  hood.  What  is  the  gas  given  off?  When  the 
action  is  over  and  the  mass  has  cooled  down,  pour 
upon  it  a  little  hot  water  and  heat  it  for  a  while  on 
the  water-bath.  Most  of  the  black  deposit  will  dis- 
solve. Filter  the  hot  solution  and  let  it  crystallize. 
What  is  the  appearance  of  the  salt  ?  Does  it  contain 
water  of  crystallization  ?  Heat  a  little  in  an  arsenic- 
tube  :  what  changes  take  place  ?  Dry  some  of  it  and 
put  it  aside  for  further  use.  Write  the  equations 
representing  the  reaction  of  copper  and  sulphuric 
acid. 

EXPERIMENT  136. 

Test-tubes  ;  barium  chloride  ;  lead  nitrate  ;  strontium  nitrate  ;  cal- 
cium chloride ;  dilute  sulphuric  acid ;  iron  sulphate ;  copper 
sulphate  ;  sodium  sulphate ;  potassium  sulphate  ;  dilute  nitric 
and  hydrochloric  acids. 

To  dilute  solutions  of  barium  chloride,  lead  nitrate, 
and  strontium  nitrate,  in  test-tubes,  add  a  little  dilute 
sulphuric  acid :  a  white  precipitate  is  formed  in  each 
case.  Write  the  equations  which  represent  the  re- 
spective reactions.  What  is  left  in  solution?  Add 
more  water  and  see  whether  the  precipitates  dissolve 
at  all.  To  a  somewhat  concentrated  solution  of  cal- 
cium chloride  add  a  few  drops  of  dilute  sulphuric 
acid :  calcium  sulphate  is  precipitated.  What  is  left 
in  solution  ?  Does  addition  of  more  water  cause  the 
precipitate  to  dissolve  ?  The  formulas  of  the  salts 
used  are,  respectively,  BaCl2 ,  Pb(NO3)a ,  Sr(NO3)a ,  and 
CaCla. 


112  CARBONATES. 

EXPERIMENT  136— Continued, 

Make  dilute  solutions  of  iron  sulphate,  FeSO4 ; 
copper  sulphate,  CuSO4 ;  sodium  sulphate,  Na2SO4 ; 
potassium  sulphate,  K2SO4.  Add  these  successively 
to  dilute  solutions  of  barium  chloride,  of  lead  nitrate, 
of  strontium  nitrate.  Is  the  action  of  the  soluble  sul- 
phates similar  to  that  of  the  sulphuric  acid  ?  Write 
the  equations  expressing  the  reactions.  What  is  left 
in  solution  ? 

Is  barium  sulphate  soluble  in  dilute  hydrochloric 
or  nitric  acid  ?  Try  it.  Is  lead  sulphate  ?  Is  stron- 
tium sulphate  ?  Is  calcium  sulphate  ? 

SEDUCTION   OF   SULPHATES. 
EXPERIMENT  137. 

Charcoal ;  blowpipe  ;  sodium  sulphate  ;  copper  sulphate  ;  silver  coin. 
Mix  and  moisten  a  little  sodium  sulphate  and  finely 
powdered  charcoal.  Heat  the  mixture  for  some  time 
in  the  reducing  flame  ;  is  a  gas  evolved  ?  When  the 
mass  is  cool  dissolve  it  in  a  little  water  and  filter. 
Add  a  little  to  a  dilute  solution  of  copper  sulphate 
and  boil ;  what  is  the  result  ?  Will  treatment  with  a 
solution  of  sodium  sulphate  produce  the  same  result  ? 
Try  it.  Put  a  few  drops  of  the  sulphide  solution  on 
a  bright  silver  coin  :  what  result  is  produced  ?  Will 
a  solution  of  sodium  sulphate  produce  this  result? 

Try  it. 

CARBONATES. 

EXPERIMENT  138. 

Test-tubes ;  copper  sulphate  ;  iron  sulphate  ;  lead  nitrate  ;  silver 
nitrate ;  calcium  chloride  ;  barium  chloride  ;  sodium  carbonate  ; 
potassium  carbonate ;  ammonium  carbonate  ;  dilute  acid  ;  lime- 
water. 

Make  solutions  of  copper  sulphate,  iron  sulphate, 


SILICATES.  113 

EXPERIMENT  138—  Continued. 

lead  nitrate,  silver  nitrate,  calcium  chloride,  and 
barium  chloride.  Add  to  each  a  little  of  a  solution  of 
a  soluble  carbonate,  as  sodium  carbonate,  potassium 
carbonate,  or  ammonium  carbonate.  What  result  is 
there  ?  Filter  off  each  of  the  precipitates  in  turn, 
wash  it  thoroughly  [Why  ?]  and  determine  whether  it 
is  a  carbonate.  For  this  purpose  treat  it  with  a  dilute 
acid ;  if  the  precipitate  is  a  carbonate,  carbon  dioxide 
will  be  given  off  and  may  be  identified  by  passing  it 
through  lime-water. 

Write  the  equations  expressing  the  reactions  you 
have  brought  about.  In  order  that  the  insoluble 
carbonate  might  be  formed  through  the  interaction  of 
the  two  soluble  salts,  the  metals  of  the  salts  have  ex- 
changed places  :  thus,  for  example, 

CuSO4  +  Na2CO3  =  CuCO3  +  Na2SO4 . 

The  formulas  of  the  salts  in  the  order  given  are  : 
CuS04 ,  FeSO4 ,  Pb(N03)2 ,  AgNO3 ,  CaCl, ,  BaCl2 ,  Na2 
CO3 ,  K2CO3 ,  (NH4)2CO3.  Which  metals  are  bivalent 
in  this  series ;  which  univalent  ? 

SILICATES. 
EXPERIMENT  139. 

Platinum  crucible  or  dish  ;   blast-lamp  ;    sand  ;   sodium  carbonate  ; 
potassium  carbonate  ;  beaker. 

Mix  together  equal  small  quantities  of  sodium  and 
potassium  carbonates,  heat  them  together  in  a  plati- 
num crucible  or  dish  in  the  flame  of  a  blast-lamp  until 
they  melt  to  a  clear  liquid.  Now  add,  a  little  at  a 
time,  fine  sand,  waiting  until  one  portion  has  dissolved 


114  SILICIC  ACID— POTASSIUM. 

EXPERIMENT  139—  Continued. 

before  adding  another.  When  the  sand  no  longer  dis- 
solves in  the  hot  molten  carbonates,  let  the  crucible 
cool  and  then  put  it  into  a  little  boiling-hot  water  in  a 
beaker.  The  sodium  and  potassium  silicates  will  pass 
into  solution.  (See  Experiment  140.) 

SILICIC   ACID. 
EXPERIMENT  140. 

Test-tube  ;   solution  of  silicates  obtained  in   last  experiment ;    sul- 
phuric or  hydrochloric  acid  ;  water-bath  ;  evaporating-dish. 

Treat  a  little  of  the  solution  containing  sodium  and 
potassium  silicates,  prepared  in  the  last  experiment, 
with  a  little  sulphuric  or  hydrochloric  acid.  A  ge- 
latinous substance  will  be  precipitated  :  this  is  silicic 
acid.  Some  of  the  acid  remains  in  solution.  By 
evaporating  the  solution  to  dryness  and  heating  for  a 
time  on  the  water-bath,  all  the  silicic  acid  is  converted 
into  silicon  dioxide,  which  is  entirely  insoluble. 
Write  the  equations  representing  the  reactions  in- 
volved in  passing  from  the  sand  to  the  silicates,  to 
the  silicic  acid,  to  the  silicon  dioxide,  or  silicic  anhy- 
dride. 

POTASSIUM. 
EXPERIMENT  141. 

Wood-ashes  ;  filter  ;   red  litmus-paper  ;  potassium  carbonate  ;  evap- 
orating-dish ;  water-bath  ;  test-tube;  dilute  hydrochloric  acid. 

1.  Treat   two   or  three   litres   of   wood-ashes   with 
water.     Filter   off  the    solution,  and   examine   it   by 
means  of  red  litmus-paper :  is  the  solution  alkaline  ? 

2.  Examine   some  potassium   carbonate :    does   its 
solution  act  in  the  same  way  ? 


POTASSIUM.  115 

EXPERIMENT  141 — Continued. 

3.  Evaporate  to  dryness  the  solution  obtained  from 
the  wood-ashes.  Collect  the  dry  residue  and  treat  it 
in  a  test-tube  with  a  little  dilute  hydrochloric  acid :  is 
a  gas  given  off  ?  What  gas  is  it  ? 

EXPERIMENT  141«. 

Potassium;  red  litmus-paper. 

Throw  a  small  piece  of  potassium  not  more  than  a 
fourth  as  large  as  a  pea,  upon  water :  what  takes 
place  ?  What  is  the  color  of  the  flame  ? 

What  difference  is  there  between  the  action  of 
sodium  and  of  potassium  on  water  ? 

Is  the  solution  after  the  action  alkaline  ?     Why  ? 

EXPERIMENT  142. 

Test-tabes  ;  crystallized  potassium  iodide  ;  iodine  ;  concentrated  sul- 
phuric acid. 

1.  Examine  a  bottle  of  crystallized  potassium  iodide. 
Taste  a  little.     Dissolve  one  or  two  of  the  crystals  in 
water. 

2.  Add  some  iodine  to  the  solution  :  does  the  iodine 
dissolve  ? 

3.  Powder  a  little  of  the  salt  in  a  dry  mortar,  press 
it  between  layers  of  filter-paper  and  afterwards  heat 
it  gently  in  a  test-tube  :  does  the  substance  contain 
water  of  crystallization  ? 

4.  Treat  a  crystal  or  two  with  a  few  drops  of  con- 
centrated sulphuric  acid  in  a  test-tube  :  what  takes 
place  ? 

To  what  is  the  appearance  of  violet  vapors  due  ? 
(See  Experiment  108.) 


116  POTASSIUM. 

EXPERIMENT  143. 

Iron  sauce-pan  ;   stout  iron  wire  or  spatula ;   potassium  carbonate  ; 
quick-lime ;  glass  siphon. 

1.  Dissolve  25  grams  potassium  carbonate  in  250- 
300  cc.  water.     Heat  to  boiling  in  an  iron  (or  silver) 
vessel,  and  gradually  add  slaked  lime  made  from  12- 
15  grams  good  quick-lime.*    During  the  operation  the 
mass  should   be   stirred  with   a  stout   iron  wire   or 
spatula. 

2.  Allow  the   solution  to   cool  without  being   dis- 
turbed.    The   insoluble    powder  will  settle   and   the 
supernatant  solution  may  now  be  drawn  off  by  means 
of  a  glass  siphon  into  a  bottle.     This  liquid  may  be 
used  in  experiments  in  which  caustic  potash  is  re- 
quired. 

Explain  what  has  taken  place. 

Write  the  equation  expressing  the  chemical  change. 

What  is  left  in  the  iron  vessel  ? 

EXPERIMENT  144. 

Iron  dish;  beaker;  test-tubes;  pink  litmus-paper;  potassium  nitrate; 
powdered  charcoal;  dilute  acid. 

1.  Mix   thoroughly  together   15   grams   potassium 
nitrate  and  2.5  grams  powdered  charcoal.     Place  the 
mixture  in  an  iron  dish  under  the  hood  and  set  fire  to  it. 

What  is  given  off?     What  is  gunpowder  made  of? 
What  is  the  cause  of  its  explosive  power  ? 

2.  What  is  left  ?     Dissolve  the  residue  in  a  little 
warm  water,  filter,  and  examine   with   pink   litmus- 
paper.     Is  it  alkaline  ?     Is  a  solution  of  potassium 
nitrate  alkaline  ?     Try  it.     Add  to  the  solution  a  little 
dilute  acid  :  what  takes  place  ?     Add  some  of  the  same 
acid  to  a  solution  of  nitre  :  what  takes  place  ? 

*  See  Experiment  60. 


AMMONIUM  SULPHIDE.  117 

SODIUM  CARBONATE;  SOLVAY  PROCESS. 
EXPERIMENT  145. 

Beaker;  test-tubes;  carbon- dioxide  generator;  dilute  ammonia;  com- 
mon salt;  arsenic-tube;  dilute  acid. 

1.  Dissolve  common  salt  in  about  50  cc.  cold  dilute 
ammonia-water  until  the  solution  will  take  up  no  more. 
Filter  the  solution  and  continue  to  pass  carbon  diox- 
ide into  it  until  the  precipitate  ceases  to  form.     Use  a 
funnel  attached  to  the  delive^-tube  as  in  Experiment 
59.     Filter  off  the  precipitate  formed  and  dry  it  by 
pressing  it  between  layers  of  filter-paper. 

2.  Heat  some  of  the  dry  salt  in  an  arsenic-tube  and 
determine  whether  carbon  dioxide  is  given  off  or  not. 
When  gas  is  no  longer  given  off,  transfer  the  residue 
to  a  test-tube  and  treat  it  with  a  dilute  acid :  is  it  a 
carbonate  ? 

VOLATILITY   OF  AMMONIUM   SALTS. 
EXPERIMENT  146. 

Platinum-foil  or  porcelain  dish;  ammonium  chloride. 

On  a  piece  of  platinum-foil  or  in  a  clean  porcelain 
dish  heat  a  little  pure  ammonium  chloride  under  a 
hood.  It  will  pass  off  and  form  a  dense  white  cloud. 
This  is  the  same  cloud  as  that  formed  by  bringing  to- 
gether gaseous  ammonia  and  hydrochloric  acid.  All 
ammonium  salts  are  volatile  or  decompose  when 
heated.  Is  potassium  chloride  volatile  ?  Is  sodium 
chloride  ? 

AMMONIUM   SULPHIDE. 
EXPERIMENT  147. 

Beaker;  hydrogen-sulphide  generator;  concentrated  ammonia-solution. 

Saturate  50  cc,  strong  aqueous  ammonia  with  hydro- 


118  FLAME  REACTIONS. 

EXPERIMENT  147—  Continued. 

gen  sulphide.*  The  liquid  will  gradually  lose  the 
sharp  odor  of  ammonia  and  will  begin  to  smell  of  the 
hydrogen  sulphide,  before  saturation  is  complete. 
Then  add  50  cc.  more  of  the  same  ammonia.  The 
liquid  is  now  a  solution  of  ammonium  sulphide.  Put 
it  in  a  bottle  for  future  use. 

INSOLUBLE   POTASSIUM  SALTS. 
EXPERIMENT  148. 

Test-tubes;  potassium  chloride;  platinum  chloride;  fluorsilicic  acid; 

alcohol. 

Make  a  rather  strong  solution  of  potassium  chloride. 
To  one  portion  of  it  add  platinum-chloride  solution  ; 
to  another  a  solution  of  fluorsilicic  acid.  If  in  the 
former  case  no  precipitate  is  formed,  add  a  little  alco- 
hol ;  potassium  chlorplatinate  is  slightly  soluble  in 
water,  but  is  insoluble  in  alcohol.  Potassium  fluor- 
silicate  is  precipitated  only  from  rather  concentrated 
solutions,  and,  even  from  these,  as  a  rule,  only  after 
standing  for  a  while.  Describe  the  appearance  of  the 
precipitates. 

FLAME   KEACTIONS. 
EXPERIMENT  149. 

Platinum  wire;  sodium,  potassium,   lithium,   caesium,  and  rubidium 

salts. 

1.  Prepare  some  pieces  of  platinum  wire  8-10  cm. 
long,  with  a  loop  on  the  end,  like  those  described  for 
blowpipe  work.  After  thoroughly  cleaning  them,  in- 
sert one  in  a  little  sodium  carbonate,  and  notice  the 
color  produced  on  inserting  it  in  the  flame. 

*  See  note,  Experiment  115, 


CALCIUM  HYDROXIDE.  119 

EXPERIMENT  149—  Continued. 

2.  Try  another  wire  with  potassium  carbonate,  and, 
if  the  substances  are  available,  others  with  a  lithium, 
a  caesium,  and  a  rubidium  compound. 

CALCIUM   CHLOKIDE. 
EXPERIMENT  150. 

Limestone  or  marble;  concentrated  hydrochloric  acid;  evaporating- 
dish;  water-bath;  concentrated  sulphuric  acid. 

1.  Dissolve  10-20  grams  of  limestone  or  marble  in 
concentrated  hydrochloric  acid.     Evaporate  *to  dry- 
ness.     Expose  a  few  pieces  of  the  residue  to  the  air : 
does  it  become  moist  ? 

In  what  experiments  has  calcium  chloride  been  used, 
and  for  what  purposes  ? 

2.  What  would  happen  if  concentrated  sulphuric 
acid  were  addsd  to  calcium  chloride  ?     Try  it. 

Explain  what  takes  place.  Is  the  residue  soluble 
or  insoluble  in  water? 

How  could  you  tell  whether  a  given  substance  is 
calcium  chloride,  sodium  chloride,  potassium  chloride, 
or  ammonium  chloride? 


CALCIUM   HYDKOXIDE. 
EXPERIMENT  151. 

Bottle;  quick-lime;  dilute  sulphuric  acid. 

1.  To  40-50  grams  good  quick-lime  add,  a  little  at  a 
time,  100  cc.  water  :  what  takes  place  ? 

2.  Afterwards  dilute  to  2  to  3  litres  and  put  the 
whole  in  a  well-stoppered  bottle.     The  undissolved 
lime  will  settle  to  the  bottom,  and  in  the  course  of 


120  PLASTER  OF  PARIS. 

EXPERIMENT  151— Continued. 

some   hours   the   solution    above  will   become  clear. 
Carefully  pour  off  some  of  the  clear  solution. 

What  takes  place  when  some  of  the  solution  is  ex- 
posed to  the  air  ?  When  the  gases  from  the  lungs  are 
passed  through  it  ?  When  carbon  dioxide  is  passed 
through  it  ? 

What  takes  place  when  dilute  sulphuric  acid  is 
added  to  lime-water? 

Is  calcium  sulphate  difficultly  or  easily  soluble  in 
water  ? 

Has  lime-water  an  alkaline  reaction  ? 

What  reaction  would  you  expect  to  take  place  be- 
tween lime  and  nitric  acid  ? 

LIME-WATER  A  SOLUBLE  HYDBOXIDE. 
EXPERIMENT  152. 

Test-tubes  ;  lime-water  ;  ferric  chloride  ;  copper  nitrate  ;  lead  nitrate. 

1.  Add  lime-water  to  a  solution  of  ferric  chloride 
until  a  precipitate  is  formed.     Boil  the  solution.     De- 
scribe the  results. 

2.  Treat  a  solution  of  copper  nitrate  in  the  same 
way  :  what  result  is  there  ? 

3.  Treat  a  solution  of  lead  ritrate  in  the  same  way  : 
what  result  is  obtained  ? 

PLASTER  OF   PARIS. 
EXPERIMENT  153. 

Porcelain  dish,  or  crucible  ;  air-bath  ;  powdered  gypsum. 
Heat   some   powdered  gypsum   for   some   time   at 
about  170°,  in  an  air-bath.     Examine  the  residue  and 
see  whether  it  will  become  solid  when  mixed  with  a 
little  water  so  as  to  form  a  paste, 


NORMAL   CALCIUM  PHOSPHATE.  121 

GYPSUM  DECOMPOSED  BY  ALKALI  CARBONATE. 
EXPERIMENT  154. 

Beaker  ;  test-tubes  ;  filter ;   powdered  gypsuin  ;    ammonium  carbon- 
ate ;  dilute  hydrochloric  acid  ;  barium  chloride. 

Upon  a  gram  or  two  of  powdered  gypsum  pour, 
say,  50  cc.  of  a  moderately  strong  solution  of  am- 
monium carbonate.  After  a  few  hours,  pour  the 
liquid  through  a  filter,  wash  the  precipitate  into  the 
filter  and  rinse  it  with  water.  See  whether  it  has 
been  changed  to  carbonate.  If  it  has,  then  there 
must  be  some  sulphate  in  the  filtrate  along  with  the 
excess  of  ammonium  carbonate.  We  usually  examine 
for  a  sulphate  by  adding  a  soluble  barium  salt,  when, 
if  a  soluble  sulphate  is  present,  barium  sulphate  is 
precipitated.  In  this  case,  Jiowever,  the  ammonium 
carbonate  would  react  with  the  soluble  barium  salt 
and  form  barium  carbonate  which,  like  the  sulphate, 
is  insoluble  in  water.  We  therefore  first  add  dilute 
hydrochloric  acid ;  this  will  convert  the  ammonium 
carbonate  into  ammonium  chloride.  On  addition  of 
barium  chloride  to  a  solution  acid  with  hydrochloric 
acid,  a  precipitate  will  indicate  the  presence  of  a 
soluble  sulphate. 

Doas  a  precipitation  occur  in  this  case  ? 

NORMAL   CALCIUM   PHOSPHATE. 
EXPERIMENT  155. 

Test-tubes  ;  calcium  chloride  :   disodium  phosphate  ;   ammonia  ;  di- 
lute acid. 

To  a  solution  of  calcium  chloride  add  disodium 
phosphate  and  ammonia  ;  what  is  the  result  ?  Add  a 


122  INSOLUBLE  SALTS  OF  ZINC. 

EXPERIMENT  155— Continued. 

dilute  acid  (nitric  or  hydrochloric) :  is  the  precipitate 
dissolved  ? 

The  reason  for  the  addition  of  the  ammonia  is  this : 
The  sodium  phosphate  which  is  used  in  laboratories 
is  the  secondary  salt,  Na2HPO4.  If  this  substance 
alone  is  added  to  a  solution  of  calcium  chloride,  the 
calcium  is  for  the  most  part  precipitated  as  the 
normal  salt,  Ca3(PO4)2 ,  but  part  remains  in  solution. 
Complete  precipitation  is  produced  by  the  addition  of 
ammonia. 

ZINC   OXIDE. 
EXPERIMENT  156. 

Charcoal ;  piece  of  zinc. 

Heat  a  small  piece  of  zinc  on  charcoal  in  the  oxidiz- 
ing flame  of  the  blowpipe.  The  white  fumes  of  zinc 
oxide  will  be  seen  and  the  charcoal  will  be  covered 
with  a  film  which  is  yellow  while  hot,  but  becomes 
white  on  cooling. 

What  element  gives  a  film  which  is  white  both  when 
hot  and  when  cold  ?  What  elements  give  a  film  which 
is  yellow  both  when  hot  and  when  cold  ? 

INSOLUBLE   SALTS   OF  ZINC. 
EXPERIMENT  157. 

Test-tubes  ;  zinc  sulphate ;  sodium  hydroxide,  carbonate,  and  phos- 
phate ;  ammonium  sulphide  ;  dilute  hydrochloric  acid. 

Try  in  succession  the  action,  upon  solutions  of  zinc 
sulphate,  of  solutions  of  sodium  hydroxide,  sodium 
carbonate,  sodium  phosphate,  and  ammonium  sul- 
phide. What  effect  does  the  addition  of  an  excess  of 
sodium  hydroxide  have  upon  a  solution  of  a  zinc  salt  ? 


COPPER  HYDROXIDE.  123 

EXPERIMENT  157—  Continued. 

Are  any  of  these  zinc  salts  insoluble  in  dilute  hydro- 
chloric acid  ?  Will  any  one  of  them  be  precipitated 
so  long  as  the  zinc  solution  is  acid  ? 

PRECIPITATION   OF  METALLIC   COPPER. 
EXPERIMENT  158. 

Test-tubes  ;  copper  sulphate  ;  strips  of  zinc  and  of  iron. 

1.  In  a  solution  of  copper  sulphate  hang  a  clean 
strip  of   zinc  :  the  zinc  will  become  covered  with  a 
layer  of  copper  and  zinc  will  pass  into  solution  as 
zinc  sulphate.     The  zinc  simply  displaces  the  copper 
in  this  case,  as  it  displaces  hydrogen  from  sulphuric 
acid.     "Write  both  equations. 

2.  Perform    a  similar   experiment,  using   a   bright 
strip  of  sheet-iron  instead  -of  the  zinc :   what  is  the 
result?     Has  iron  gone  into   solution?     If   so,  how 
could  you  prove  it  ? 

COPPER  HYDROXIDE. 
EXPERIMENT  159. 

Test-tube  ;  copper  sulphate  ;  caustic  soda  or  potash. 

Add  some  caustic  soda  or  potash  to  a  small  quan- 
tity of  a  cold  solution  of  copper  sulphate  in  a  test- 
tube  :  what  do  you  notice  ? 

After  noticing  the  appearance  of  the  precipitate 
first  formed,  heat.  What  change  takes  place?  Ex- 
plain this. 

Express  the  chemical  change  by  the  proper  equation. 


124:  ANALYSIS  OF  COIN-SILVER. 

COPPER  SULPHIDE. 
EXPERIMENT  160. 

Copper  sulphate  ;    hydrochloric   acid  ;    hydrogen  sulphide ;    dilute 
nitric  acid  ;  ammonia  ;  ammonium  sulphide. 

1.  Prepare  a  dilute  solution  of  copper  sulphate  and 
pass  hydrogen  sulphide  through  it  for  some  time  : 
what  change  in  color  takes  place  ? 

T^he  insoluble  substance  formed  is  copper  sulphide, 
CuS.     Is  it  soluble  in  dilute  hydrochloric  acid  ? 

2.  Filter  and  wash.     Treat  with  dilute  nitric  acid. 
Is  the  sulphide  dissolved  ? 

3.  Add  ammonia  to  this  solution :  what  effect  has 
this  upon  the  color  ? 

How  could  you  detect  copper  ? 

4.  Add  ammonium  sulphide  to  some  of  the  solution 
of  copper  sulphate.     Compare  the  result  with  that 
obtained  with  hydrogen  sulphide.     Write  the  equa- 
tions expressing  both  reactions. 

DEPOSITION  OF  METALLIC  MERCURY. 
EXPERIMENT  160#. 

Test-tube;  mercury  salt;  strip  of  copper. 
Into  a  solution  of  mercurous  nitrate,  or  of  any  other 
soluble  mercury  salt,  introduce  a  strip  of  bright  cop- 
per :  what  takes  place  ?     Is  the  color  of  the  solution 
affected  ?     Explain  the  results. 

ANALYSIS  OF  COIN-SILVER. 
EXPERIMENT  161. 

Silver  coin;  dilute  nitric  acid;  common  salt;  filter;  porcelain  crucible; 
small  piece  of  sheet-zinc;  dilute  sulphuric  acid;  charcoal;  evap- 
orating-dish;  water-bath;  bottle  wrapped  in  dark  paper. 

1.  Dissolve  a  10-  or  25-  cent  piece  in  warm  dilute 


ANALYSIS  OF  COIN- SILVER.  125 

EXPERIMENT  161— Continued. 

nitric  acid.     What  action  takes  place  ?     Dilute   the 
solution  to  200-300  cc.  with  water. 

What  is  the  color  of  the  solution  ?  What  does  this 
indicate  ?  Does  this  color  prove  the  presence  of  cop- 
per? 

2.  Add  a  clear  solution  of  common  salt  until  it  ceases 
to  produce  a  precipitate.     AVhat  change  takes  place  ? 

3.  Filter  off  the  white  silver  chloride  and  carefully 
wash  with  hot  water.    Dry  the  precipitate  on  the  filter, 
by  putting  the  funnel  with  the  filter  and  precipitate 
in  an  air-bath  heated  to  about  110U.     Kernove  the  pre- 
cipitate from  the  filter  and  put  it  into  a  porcelain  cru- 
cible.    Heat  gently  with  a  small  flame  until  the  chlo- 
ride is  melted  ;  then  let  it  cool. 

4.  Cut  out  a  piece  of  sheet-zinc  large  enough  to 
cover  the  bottom  of  the  crucible.     Lay  it  on  the  silver 
chloride.     Now  add  a  little  water  and  a  few  drops  of 
dilute    sulphuric  acid,  and  let  the  whole  stand   for 
twenty-four  hours. 

Wliat  takes  place?  Does  the  deposit  look  like 
silver? 

5.  Take  out  the  piece  of  zinc  and  wash  the  silver 
with  a  little  dilute  sulphuric  acid,  and  then  with  water. 
Heat  a  small  piece  of  the  metal  on  charcoal  with  the 
blowpipe  flame  until  it  melts  and  forms  a  bead.   Does 
it  resemble  silver  ? 

6.  Dissolve  the  silver  in  dilute  nitric  acid  and  evap- 
orate to  dry  ness  on  the  water-bath,  so  that  the  excess 
of  nitric  acid  is  driven  off.     Dissolve  the  residue  in 
water,  and  put  the  solution  in  either  a  bottle  of  dark 
glass  or  one  wrapped  in  dark  paper. 


126        PRECIPITATION  OF  METALLIC  SILVER. 

HALOGEN  SALTS  OF  SILVER. 
EXPERIMENT  162. 

Test-tubes;   solution  of  silver  nitrate  prepared  in  last  experiment; 
sodium  chloride;  potassium  bromide;  potassium  iodide. 

1.  To  a  few  cc.  of  water  in  a  test-tube  add  5  to  10 
drops  of  the  solution  of  silver  nitrate  just  prepared. 
To  this  dilute  solution  add  a  few  drops  of  a  solution 
of  sodium  chloride.     What  takes  place  ? 

Place  it  aside  where  the  light  can  shine  upon  it,  and 
notice  the  change  of  color  which  gradually  takes  place. 
[Is  silver  chloride  soluble  in  dilute  nitric  acid  ?  in  am- 
monia ?] 

2.  In  the  same  way  make  the  bromide  by  adding 
potassium  bromide,  and  the  iodide  by  adding  potas- 
sium iodide,  to  silver  nitrate,  and  perform  the  same 
experiments  with  them  as  with  the  chloride.    Is  either 
of  them  soluble  in  dilute  nitrio  acid  ?  in  ammonia  ? 
In  what  ways  do  they  resemble  silver  chloride  ?     In 
what  ways  are  they  different  ? 

.PRECIPITATION  OF  METALLIC  SILVER. 
EXPERIMENT  163. 

Test-tube;  silver  nitrate;  mercury. 

To  a  solution  containing  about  a  gram  of  silver 
nitrate  in  20  cc.  water  add  a  few  drops  of  mercury  and 
let  it  stand.  In  a  day  or  two  the  silver  will  be  depos- 
ited in  the  form  of  delicate  crystals.  This  formation  is 
called  the  "  silver-tree." 


SOLVENTS  FOR  ALUMINIUM.  127 

INSOLUBLE   SILVER  SALTS. 
EXPERIMENT  164. 

Test-tubes;  silver  nitrate;  sodium  hydroxide,  chloride,  carbonate,  and 
phosphate;  potassium  bromide  and  iodide;  ammonium  sulphide; 
dilute  nitric  acid;  ammonia. 

Soluble  hydroxides,  when  added  to  solutions  of  sil- 
ver salts,  precipitate  silver  oxide.  Would  you  expect 
this  precipitate  to  be  soluble  in  dilute  nitric  acid  ? 
Why?  Is  it  soluble? 

Which  of  the  insoluble  silver  salts  are  dissolved  by 
dilute  nitric  acid  ?  Which  ones  are  soluble  in  ammo- 
nia ?  To  obtain  an  answer  to  these  questions  examine 
the  chloride,  bromide,  iodide,  sulphide,  carbonate,  and 
phosphate. 

SOLVENTS   FOR  ALUMINIUM. 
EXPERIMENT  164a. 

Test-tubes  ;  metallic  aluminium ;  dilute  hydrochloric  acid  ;  caustic 

soda. 

1.  Dissolve  a  bit  of  metallic  aluminium  in  dilute 
hydrochloric  acid  :  what  is  the  gas  given  off?     What 
is  left  in  the  solution  ? 

2.  Dissolve  a  small  piece  of  aluminium  in  a  hot  so- 
lution of  caustic  soda :  what  gas  is  evolved  ?     The 
solution  contains  sodium  aluminate,  Na3AlO3.     After 
the  metal  is  completely  dissolved  add  cautiously  dilute 
hydrochloric  acid :  aluminium  hydroxide  will  be  pre- 
cipitated and,  on  addition  of  more  acid,  will  again  be 
dissolved. 


128  ALUMINIUM  HYDROXIDE. 


ALUMINIUM  HYDROXIDE. 

EXPEEIMENT   165. 

Test-tubes;  alum;  potassium  hydroxide;  sodium  hydroxide. 

1.  Precipitate  some  aluminium  hydroxide  from  a 
dilute  solution  of  alum,  by  means  of  caustic  potash, 
and  continue  to  add  the  latter  slowly,  when  the  pre- 
cipitate will  dissolve.     Write  the  equations  involved. 

2.  Do  the  same  with  caustic  soda. 

Compare  Experiment  164a,  2.  In  what  ways  do  the 
reactions  differ? 

ALUM. 
EXPERIMENT  166. 

Beaker;  test-tube;  platinum  wire;  alum;  caustic  soda. 

1.  Determine  whether  the  alum  in  the  laboratory 
contains  potassium  or  ammonium.    When  it  is  treated 
with  hot  caustic  soda  solution,  is  ammonia  evolved  ? 
Does  it  color  the  flame  ? 

2.  Heat  a  little  water  and  dissolve  alum  in  it  until 
it  will  not  take  .up  any  more.     Let  it  cool  slowly. 
What  forms  do  the  crystals  possess  ? 

ALUMINIUM  HYDROXIDE. 
EXPERIMENT  167. 

Test-tubes;  alum;  sodium  carbonate;  filter;  dilute  acid. 

Add  a  dilute  solution  of  sodium  carbonate  to  a  dilute 
solution  of  alum.  What  is  the  appearance  of  the  pre- 
cipitate? Is  a  gas  given  off?  Filter  off  the  precipi- 
tate and  wash  it  repeatedly  with  hot  water.  [Why  ?] 
Treat  it  with  a  little  dilute  acid  :  is  it  a  carbonate  ? 
How  do  you  know  ? 


DEPOSITION  OP  METALLIC  LEAD. 
EXPERIMENT  168. 

Test-tubes;  alum;  ammonium  sulphide;  filter;  dilute  acid. 

Proceed  exactly  as  in  Experiment  167,  using,  how- 
ever, ammonium  sulphide  in  the  place  of  sodium  car- 
bonate. Is  the  precipitate  a  sulphide  ?  How  do  you 
know? 

DEPOSITION   OF   METALLIC   LEAD. 
EXPERIMENT  169. 

Flask  ;  lead  nitrate  ;  dilute  nitric  acid  ;  sheet  zinc  ;  dilute  hydro- 
chloric acid  ;  hydrogen-sulphide  generator  ;  ammonia  ;  ammo- 
nium sulphide. 

1.  Dissolve  5  grams  lead  nitrate  in  half  a  litre  of 
water  to  which  a  few  drops  of  dilute  nitric  acid  have 
been  added.     If  the  solution  is  not  clear,  add  a  few 
drops  more  acid.     Wash  a  small  piece  of  sheet  zinc 
with  dilute  nitric  acid  and'  suspend  it  by  means  of  a 
string  in  the  solution.     The  lead  will  be  slowly  de- 
posited in  crystalline  form,  and  at  the  same  time  the 
zinc  will  pass  into  solution.     Compare  the  action  with 
that  of  zinc  and  iron  on  copper  sulphate  (Experiment 
158),  and  of  zinc  on  silver  chloride  (Experiment  161). 
Write  the  equation  representing  the  reaction. 

2.  Filter  off  some  of  the  solution,  add  dilute  hydro- 
chloric acid,  and  then  pass  hydrogen  sulphide  through 
it  until  the  solution  is  saturated  with  the  gas.     Filter. 
[Will  there  be  any  lead  in  the  filtrate  ?]     To  the  fil- 
trate add  ammonia  in  excess  :  was  zinc  present  in  the 
solution  ? 

Another  method  by  which  zinc  can  be  shown  to  be 
present  in  the  solution  is  this :  Add  sulphuric  acid 
and  alcohol  to  the  solution  from  which  the  lead  was 
deposited :  any  lead  still  in  solution  will  thus  be  pre- 


130  OXIDES  OF  LEAD. 

EXPEKIMENT  169—  Continued. 

cipitated  as  sulphate.  Filter,  and  to  the  filtrate  add 
ammonia  in  excess  and  ammonium  sulphide  :  the  zinc 
will  be  precipitated  as  sulphide. 

ACTION   OF  WATEE  AND   AIR  ON  METALLIC 
LEAD. 

EXPERIMENT  170. 

Sheet-lead  ;  shallow  dish  or  plate  ;   dilute  hydrochloric  acid  ;  dilute 
sulphuric  acid  ;  hydrogen  sulphide  ;  lead  acetate. 

1.  Cut  a  piece  of  sheet-lead  an  inch  or  two  square 
and  partly  cover  it  with  water  in  a  shallow  dish.     Al- 
low it  to  stand  for  several  days,  renewing  the  water 
from  time  to  time.     Then  filter  off  and  examine  the 
solution  for  lead. — 

2.  To  a  few  cc.  of  the  solution  in  a  test-tube  add 
2-3  drops  of  hydrochloric  acid. 

Is  a  precipitate  formed  ?     To  what  extent  is  lead 
chloride  soluble  in  water  ? 

3.  To  another  small  portion  of  the  solution  add  a 
few  drops  of  sulphuric  acid. 

Is  a  precipitate  formed  ?     Is  lead  sulphate  at  all 
soluble  in  water  ? 

4.  Into  a  third  portion  pass  a  little  hydrogen  sul- 
phide. 

What  takes  place  ? 

5.  Try  the  same  experiments  with   a  very  dilute 
solution  of  lead  acetate. 

OXIDES   OF  LEAD. 
EXPERIMENT  171. 

Minium,  or  red  lead  ;  dilute  nitric  acid  ;  hydrogen  sulphide. 
Treat  a  little  minium  with  ordinary  dilute  nitric 


LEAD   CHLORIDE.  131 

EXPERIMENT  111— Continued. 

acid  in  a   test-tube,  and   note  the   change  in   color. 
Filter.     Is  there  lead  in  the  nitrate  ? 
How  do  you  know  ? 

EXPERIMENT  172. 

Lead  peroxide  ;  strong  hydrochloric  acid. 

Treat  a  little  lead  peroxide  with  strong  hydrochloric 
acid  in  a  test-tube.  What  takes  place  ?  Write  the 
equation  expressing  the  reaction  which  has  taken 
place. 

In  what  form  is  the  lead  after  the  experiment? 

Is  the  product  soluble  or  insoluble  in  cold  water ; 
in  hot  water  ? 

EXPERIMENT  173. 

Wide  test-tube  ;  lead  peroxide  ;•  concentrated  sulphuric  acid. 
In  a  rather  wide  test-tube  carefully  heat  some  lead 
peroxide  with   concentrated   sulphuric   acid.      Show 
that  oxygen  is  given  off.     What  is  left  behind  ?    Is  it 
soluble  or  insoluble  ? 

LEAD   CHLORIDE. 
EXPERIMENT  174. 

Test-tube  ;   lead  nitrate  or  acetate  ;   dilute  hydrochloric  acid  ;   am- 
monia solution ;  hydrogen  sulphide. 

To  a  dilute  solution  of  lead  nitrate  or  acetate 
add  some  hydrochloric  acid.  Heat  and  thus  dissolve 
the  precipitate.  Stand  the  tube  aside  to  cool.  As 
the  solution  cools  the  lead  chloride  crystallizes  out. 
After  the  crystallization  has  ceased,  pour  off  a  little 
of  the  solution  and  pass  hydrogen  sulphide  through 
it :  is  there  still  lead  chloride  in  solution  ?  Treat  the. 


132  STANNIC  CHLORIDE. 

EXPERIMENT  174— Continued. 

crystallized  chloride  with  a  little  cold  dilute  ammonia  ; 
does  it  dissolve  ?  Would  silver  chloride  have  dis- 
solved ? 

STANNOUS   CHLOKIDE. 
EXPERIMENT  175. 

Beaker  ;  tin  ;  concentrated  hydrochloric  acid  ;  mercuric  chloride. 

Place  a  few  grams  of  tin  in  a  beaker  under  a  hood 
and  pour  upon  it  a  mixture  of  about  equal  volumes 
of  concentrated  hydrochloric  acid  and  water.  Heat 
gently  to  start  the  action.  To  part  of  the  solution  of 
stannous  chloride  thus  formed  add  a  solution  of  mer- 
curic chloride  :  a  white  precipitate  of  mercurous  chlo- 
ride will  be  formed.  Heat  the  solutions  together,  and 
notice  the  formation  of  metallic  mercury,  which  ap- 
pears as  a  gray  powder. 

What  change  has  taken  place  in  the  stannous  chlo- 
ride ? 

STANNIC   CHLORIDE. 
EXPERIMENT  176. 

Beaker ;  tin  ;  concentrated  hydrochloric  and  nitric  acids  ;  hydrogen 
sulphide  ;  ammonium  sulphide  ;  dilute  acid. 

Under  a  hood  dissolve  a  little  tin  in  aqua  regia, 
using  no  more  of  the  acid  than  is  necessary.  Make 
the  solution  very  dilute  and  pass  hydrogen  sulphide 
through  it.  Filter  off  the  precipitate,  wash  it  with 
water  and  treat  it  with  ammonium  sulphide.  Does 
the  precipitate  dissolve  ? 

Add  an  acid  to  the  solution ;  what  takes  place  ? 


ANTIMONY  AND   TIN— SOLDER.  133 

ANTIMONY   AND   TIN. 

EXPEEIMENT   177. 

Test-tubes  ;   tin  ;   antimony  ;  concentrated  nitric  acid  ;   concentrated 
hydrochloric  acid. 

1.  Treat  a  little  tin  with  concentrated  nitric  acid 
under  a  hood,  and  notice  the  formation  of  the  white 
metastannic  acid.     [Is  it  soluble  in  water  ?] 

2.  Treat  a  little  antimony  in  the  same  way  :  is  the 
action  similar  ? 

3.  Now  treat  each  with  rather  strong  hydrochloric 
acid  :  do  both  dissolve  ? 

SOLDER. 
EXPERIMENT  178. 

Beaker ;  solder  ;    aqua  regia  ;   hydrogen  sulphide  ;   ammonium  sul- 
phide ;  dilute  nitric  acid  ;  ammonium  carbonate. 

Examine  a  small  piece  of  solder,  and  by  the  follow- 
ing method  show  that  it  contains  tin  and  lead : 

1.  Treat  with  hot  aqua  regia  under  a  hood,  using  no 
more  of  the  acid  than  may  be  necessary.     What  will 
the  products  of  the  reaction  be  ? 

2.  Dilute  with  water.     [Will  all  the  lead  pass  into 
solution  under  these  circumstances ;  will  any  of  it  ?] 
Pass   hydrogen  sulphide  through  the  solution  ;  filter 
off  the  precipitate ;  wash  with  hot  water ;  treat  with 
yellow  ammonium  sulphide  on  the  filter,  and  wash 
again.     What  is  left  on  the  filter  ? 

Place  the  filter  with  the  precipitate  in  a  test-tube  or 
beaker,  and  treat  it  with  hot  dilute  nitric  acid.  Does 
the  precipitate  dissolve  ?  Filter  the  solution  and 
examine  the  filtrate  for  lead. 

3.  To  the  filtrate,  obtained  by  treating  tlie  mixed 


134  BRONZE. 

EXPERIMENT  178—  Continued. 

sulphides   with   ammonium    sulphide,   add    a   dilute 
acid  :  what  is  the  result  ? 

Tin  sulphide  and  arsenic  sulphide  are  both  soluble 
in  ammonium  sulphide  and  are  reprecipitated  on  the 
addition  of  an  acid  to  the  solution.  Arsenic  sulphide 
dissolves  in  the  same  way  in  ammonium  carbonate 
also ;  tin  sulphide  does  not.  Treat  some  of  the  sul- 
phide therefore  with  ammonium  carbonate  solution, 
filter,  and  add  an  acid.  Is  a  precipitate  formed  ? 
Does  solder  contain  arsenic  ? 


BRONZE. 
EXPERIMENT  179. 

Beaker;  bronze;  aqua  regia;  hydrogen  sulphide  ;  ammonium  sul- 
phide ;  dilute  nitric  acid  ;  ammonium  carbonate  ;  sodium  hy- 
droxide solution  ;  sodium  carbonate. 

Examine  a  small  piece  of  bronze,  and  show  by  the 
following  method  that  it  contains  tin  and  copper : 

1.  Dissolve  in  hot  aqua  regia,  using  no  more  acid 
than  is  necessary ;   dilute  with  water ;  saturate  with 
hydrogen  sulphide ;  filter  through  a  well-fitting  filter. 
If  the  liquid  is  not  clear  after  filtration,  pass  it  again 
through  the  same  filter.     Wash  the  precipitate  with 
water  and  then  treat  it  on  the  filter  with  ammonium 
sulphide.     Wash  the  residue  with  water. 

2.  To  the  filtrate  containing   the  ammonium   sul- 
phide,   add   a   dilute    acid :    what    result    is    there  ? 
Prove  that  the  precipitate  is  tin  sulphide  and  not 
arsenic  sulphide. 

3.  Dissolve  the  residue  insoluble  in  ammonium  sul- 
phide, in  hot  dilute  nitric  acid,  and  filter.    Treat  a 


iTOFffi 

r. 


IRON.  135 

EXPERIMENT  1 79 —  Continued. 

portion  of  the  solution  of  copper  nitrate  thus  formed 
with  an  excess  of  caustic  soda,  boil,  and  filter. 

Explain  the  results.  Mix  some  of  the  black  pre- 
cipitate with  dry  sodium  carbonate,  and  heat  in  the 
reducing  flame  of  the  blowpipe.  What  evidence  do 
you  get  of  the  presence  of  copper  ? 

IRON. 

EXPERIMENT    180. 

Small  flask  ;  test-tubes  ;  iron  wire  or  turnings  ;  dilute  hydrochloric 
acid  ;  solution  of  sodium  hydroxide  ;  concentrated  nitric  acid ; 
zinc. 

1.  Dissolve  a  little  iron  wire  or  turnings  in  dilute 
hydrochloric  acid.     What  is  given  off?     The  odor  is 
due  to  certain  carbon  compounds  contained  in  the 
iron. 

What  remains  undissolved  ?  What  is  in  solution  ? 
Write  the  equation  representing  the  action  of  the  acid 
on  the  iron. 

2.  To  a  little  of  the  solution  in  a  test-tube  add  at 
once  a  solution  of  sodium  hydroxide  :  ferrous  hydrox- 
ide is  precipitated.     What  is  its  appearance  ?     Write 
the  equation  expressing  the  reaction. 

3.  Let  the  tube  containing  the  hydroxide  precipitate 
stand  open,  and  shake  it  up  from  time  to  time  :  what 
changes  do  you  notice  ? 

Explain  what  you  have  seen. 

4.  Heat  another  portion  of  the  solution  of  ferrous 
chloride  to  boiling ;  then  add  a  few  drops  of  concen- 
trated nitric  acid,  and  boil  again.     Repeat  this  two  or 
three   times.      What   change   in   color   takes   place? 
What  is  now  in  solution  ? 


136  POTASSIUM  PERMANGANATE. 

EXPERIMENT  180— Continued. 

Add  caustic  soda  to  the  solution  :  what  is  formed  ? 
What  is  the  chemical  change  ? 

Compare  the  precipitate  with  that  in  the  tube  which 
you  have  put  aside  (see  3). 

5.  Just  as  in  this  case  we  have  passed  from  ferrous 
chloride  to  ferric  chloride  by  oxidation,  so  we  can 
pass  back  again  to  the  ferrous  compound. 

Thus,  to  the  solution  of  ferric  chloride  add  a  little 
dilute  hydrochloric  acid  and  some  small  pieces  of 
zinc :  does  the  green  color  return  ?  Examine  with 
caustic  soda  :  is  ferrous  chloride  present  ? 


POTASSIUM  PERMANGANATE. 
EXPERIMENT  181. 

Porcelain  crucible  ;  potassium  hydroxide  ;  powdered  manganese  di- 
oxide ;  potassium  chlorate  ;  beaker  ;   dilute  acid. 

1.  In  a  small  porcelain   crucible  heat  together  5 
grams  powdered  manganese  dioxide,  5  grams  solid 
caustic   potash,  and   2.5   grams   potassium    chlorate. 
The  mass  will  melt  and  turn  green.     When  it  seems 
to  have  come  to  a  uniform  consistency,  let  the  crucible 
cool. 

2.  Heat  150-200  cc.  water  to  .boiling  in  a  beaker ; 
remove  the  burner,  and  place  the  crucible  in  the  hot 
water  until  the  contents  are  dissolved.     Add  dilute 
acid  until  most  of  the  excess  of  alkali  has  been  neu- 
tralized :  the  green  solution  of  potassium  manganate 
will  change  to  a  purple  solution  of  potassium  perman- 
ganate. 


POTASSIUM  DICHROMATE.  137 

EXPERIMENT  182. 

Test-tubes :  potassium  permanganate  solution  prepared  in  last 
Experiment ;  dilute  sulphuric  acid  ;  ferrous  sulphate  ;  solution 
of  sulphur  dioxide  in  water  ;  concentrated  hydrochloric  acid. 

1.  To  a  dilute  solution  of  ferrous  sulphate  contain- 
ing free  sulphuric  acid,  add  drop  by  drop  some  of  the 
solution  of  potassium   permanganate  :  is   the   purple 
color   destroyed?      Does   the    solution   now   contain 
ferrous  salt? 

2.  Add  permanganate  solution  to  a  solution  of  sul- 
phur dioxide  in  water  :  is  the  color  destroyed?    Does 
the  solution  still  smell  of  sulphur  dioxide  ? 

3.  Add  a   little  concentrated  hydrochloric  acid  to 
some  of  the  permanganate  solution,  and  heat.     What 
do  you  notice  ?     Explain  the  change. 

POTASSIUM  CHROMATE. 
EXPERIMENT  183. 

Iron  crucible  ;  powdered  chrome  ore  ;  potassium  hydroxide ;  potas- 
sium carbonate  ;  potassium  nitrate. 

Heat  together  in  an  iron  crucible  over  a  blast-lamp 
about  5  grams  each  of  potassium  hydroxide,  potassium 
carbonate,  and  potassium  nitrate.  To  the  molten 
mass  add  gradually  5  grams  finely-powdered  chrome 
ore,  and  stir  until  further  heating  produces  no  more 
change.  Let  the  crucible  cool  and  then  dissolve  the 
contents  in  hot  water.  Keep  the  solution  of  potassium 
chromate  thus  prepared. 

POTASSIUM   DICHROMATE. 
EXPERIMENT  184. 

Solution  of  potassium  chromate  prepared  in  the  last  Experiment ; 
concentrated  nitric  acid. 

To  some  of  the  solution  of  potassium   chromate 


138  INSOLUBLE  CHROMATES. 

EXPERIMENT  184—  Continued. 

already  obtained,  add,  drop  by  drop,  concentrated 
nitric  acid  until  the  potassium  nitrite  and  carbonate 
present  have  been  decomposed  and  the  solution  has  a 
decided  acid  reaction :  the  color  will  change  from 
yellow  to  red.  The  red  color  indicates  the  presence 
of  the  dichromate. 

POTASSIUM  DICHROMATE  AND  CHROMATE. 
EXPERIMENT  185. 

Beaker ;  potassium  dichromate  ;  potassium  hydroxide  ;  water-bath. 

Make  a  hot,  rather  concentrated  solution  of  potas- 
sium dichromate  (10-20  grams).  To  this  add  a  rather 
strong  solution  of  potassium  hydroxide  until  the  red 
color  is  entirely  changed  to  yellow.  Evaporate  to 
crystallization.  The  salt  formed  is  potassium  chro- 
mate.  Keep  the  crystals. 

SALTS    OF    CHROMIC   ACID    AS    OXIDIZING 

AGENTS. 
EXPERIMENT  186. 

Test-tubes  ;    potassium  cliromate  ;    potassium  dichromate  ;    concen- 
trated hydrochloric  acid. 

In  test-tubes  treat  dry  potassium  chromate  and  dry 
potassium  dichromate  each  with  concentrated  hydro- 
chloric acid.  What  evidence  do  you  get  that  the  salts 
are  good  oxidizing  agents?  Write  the  equations 
representing  the  reactions. 

INSOLUBLE  CHROMATES. 
EXPERIMENT  187. 

Potassium  chromate  or  dichromate ;   barium  chloride ;  lead  acetate 
or  nitrate  ;  potassium  or  sodium  sulphate  ;  dilute  nitric  acid. 

1,  Adcj.  a  little  of  a  solution  of  potassium  chromate 


CHROMIUM  AS  A  BASE-FORMING  ELEMENT.    139 

EXPERIMENT  187—  Continued. 

or  dichromate  to  a  solution  of  barium  chloride,  and 
to  a  clear  solution  of  lead  acetate  or  nitrate. 

Explain  what  takes  place. 

Treat  each  with  dilute  nitric  acid  ;  what  result  ? 

2.  Do  the  same  thing  using  potassium  or  sodium 
sulphate   instead   of   potassium   chromate.     How  do 
the   results   compare   with  those    obtained  with   the 
chromate  ?      Do    sulphur   and  chromium   belong   to 
the  same  Group  in  Mendeleeff's  Scheme  ? 

Compare  the  composition  of  chromic  acid  with  that 
of  sulphuric  acid.     What  resemblance  is  there  ? 

3.  How,  by   the  aid   of   barium-chloride    solution, 
could  you  distinguish  between  a  sulphate  and  a  chro- 
mate ? 

CHROMIUM  AS  A  BASE-FORMING  ELEMENT. 
EXPERIMENT  188. 

Test-tubes  ;  potassium  dicliromate  ;  concentrated  hydrochloric  acid  ; 
alcohol  ;  ammonia ;  ammonium  sulphide  ;  sodium  carbonate  ; 
sodium  hydroxide. 

1.  To  a  solution  of  potassium  dicliromate  add  some 
rather  strong  hydrochloric  acid  and  a  little  alcohol. 
On  boiling  the  alcohol  takes  up  oxygen  from  the  di- 
cliromate, a  peculiar-smelling  substance,  aldehyde,  is 
given  off,  and   the   solution  now  contains   chromium 
chloride,  CrCl3.     The  solution  has  a  green  color.     The 
change  is  represented  thus  : 

K2CraO7  +  3C2H60  +  8  HC1  = 

Alcohol. 

2KC1  +  2CrCl3+3C2H4O  +  7H2O. 

Aldehyde. 

2.  To  separate  portions  of  the  diluted  solution  add 


140  FERMENTATION  OP  GLUCOSE. 

EXPERIMENT  188—  Continued. 

ammonium  sulphide,  sodium  carbonate,  and  sodium 
hydroxide,  respectively.  The  reaction  in  each  case 
yields  chromium  hydroxide. 

Write  the  equations.  In  the  first  reaction  hydro- 
gen sulphide  is  evolved ;  in  the  second,  carbon  diox- 
ide. (Compare  Experiments  165,  167,  and  168.) 

3.  To  the  precipitate  formed  with  caustic  soda  add 
an  excess  of  the  reagent ;  does  the  precipitate  dis- 
solve ?  Boil  the  solution  ;  what  happens  ?  (Compare 
Experiment  165.) 

FERMENTATION  OF  GLUCOSE. 
EXPERIMENT  189. 

Apparatus  as   shown   in   Fig.   43 ;    commercial   grape-sugar  ;    fresh 
brewer's  yeast ;  lime-water  ;  potassium  hydroxide. 

Dissolve  about  150  grams  commercial  grape-sugar 
in  1£  litres  of  water  in  a  flask.  Connect  the  flask  by 
means  of  a  bent  glass  tube  with  a  cylinder  or  bottle 

containing  clear  lime- 
water.  The  vessel  con- 
taining the  lime-water 
must  be  provided  with  a 
cork  with  two  holes. 
Through  one  of  these 
passes  the  tube  from 
FIG.  43.  the  fermentation-flask  ; 

through  the  other  a  tube  connecting  with  a  tube  con- 
taining solid  caustic  potash,  the  object  of  which  is  to 
prevent  the  air  from  acting  upon  the  lime-water.  The 
arrangement  of  the  apparatus  is  shown  in  Fig.  43. 
Now  add  to  the  solution  of  grape-sugar  some  fresh 


ALDEHYDE— SOAP.  141 

EXPERIMENT  189—  Continued. 

brewer's  yeast ;  close  the  connections  tight  and  allow 
the  vessels  to  stand  in  a  warm  place. 

What  changes  take  place  ?  What  is  the  most  evi- 
dent product  of  the  reaction?  What  is  left  in  the 
large  flask  ? 

Explain  all  you  have  seen. 

ALDEHYDE. 
EXPERIMENT  190. 

Small   flask  ;  potassium   dichromate  ;    concentrated  sulphuric  acid  ; 

alcohol. 

In  a  small  flask  put  a  few  pieces  of  potassium  di- 
chromate, K2Cr2O7,  and  pour  upon  it  a  few  cc.  of  moder- 
ately concentrated  sulphuric  acid.  To  this  mixture 
add  slowly  a  few  cc.  of  ordinary  alcohol.  The  odor 
of  aldehyde  will  be  noticed. 

SOAP. 
EXPERIMENT  191. 

Small  iron  pot ;  lard  ;  sodium  hydroxide  ;  common  salt. 

1.  In  a  small  iron  pot  boil  slowly  for  an  hour  or 
two  an   ounce   of   lard  with  a  solution  of  20  grams 
caustic  soda  in  250  cc.  water.     After  cooling  add  a 
strong  solution  of  common  salt. 

The  soap  is  soluble  in  water  but  not  in  salt-solu- 
tion :  it  therefore  separates  and  rises  to  the  surface. 

Write  the  equations  that  represent  the  reactions 
involved.  Glycerin  is  a  triacid  base  and  in  that  re- 
spect resembles  aluminium  hydroxide.  The  acids  with 
which  the  glycerin  is  combined  in  the  fat  are  mono- 
basic. 

2.  Dissolve  some  of  the  soap  thus  obtained  in  water. 


142  HARD  WATER-TANNIC  ACID. 

HARD  WATER. 
EXPERIMENT  1.92. 

Carbon  dioxide  ;  lime- water  ;  solution  of  soap. 

1.  Make  some  hard  water  by  passing  carbon  dioxide 
through  dilute  lime-water  until  the  precipitate  first 
formed  is  dissolved  again.     Filter. 

2.  Make  a  solution  of  soap  by  shaking  up  a  few 
shavings  of  soap  with  water.     Filter. 

3.  Add  the  solution  of  soap  to  the  hard  water.     Is 
a  precipitate  formed  ? 

4.  Rub  a  piece  of  soap  between  the  hands  wet  with 
the  hard  water.     Explain  what  you  observe. 

5.  Boil  thoroughly  part  of  the  hard  water  prepared 
as  described  above.     Filter.     Repeat  the  experiment 
with  soap-solution.     Is  the  water  still  hard  ?     Why  ? 

EXPERIMENT  193. 

Powdered  gypsum  ;  solution  of  soap  made  as  in  last  experiment. 

1.  Make  some  hard  water  by  shaking  a  litre  or  two 
of  water  with   a  little  powdered  gypsum.     Perform 
with  it  the  same  experiments  as  those  first  performed 
with  the  water  containing  calcium  carbonate. 

2.  Boil  the  hard  water,  and  examine  again. 
Is  it  still  hard?     Why? 

TANNIC    ACID. 
EXPERIMENT  194. 

Powdered  gall-nuts  ;  ferrous  sulphate. 

1.  Boil  10  grams  of  powdered  gall-nuts  with  60  cc. 
water,  adding  water  from  time  to  time.     A  solution  of 
tannin  is  thus  obtained.     After  the  solution  has  stood 
for  some  time  filter  it. 

2.  In  a  test-tube  add  to  some  of  this  solution  a  few 
drops  of  a  solution  of  copperas  (ferrous  sulphate). 

What  is  formed  ?     What  does  it  resemble  ? 


HOW  TO  ANALYZE  SUBSTANCES. 

•  In  order  to  analyze  substances  chemists  make  use 
of  reactions  such  as  have  been  studied  in  the  earlier 
parts  of  this  book.  To  learn  to  analyze  complicated 
substances,  long  practice  and  careful  study  of  a  great 
many  facts  are  necessary.  But  simple  substances  can 
be  analyzed  by  the  aid  of  such  facts  as  have  already 
been  studied.  It  has  been  seen,  for  example,  that  cer- 
tain chlorides  are  insoluble  in  water ;  that  certain 
sulphides  are  insoluble  in  dilute  hydrochloric  acid ; 
and  that  other  sulphides  which  are  soluble  in  dilute 
hydrochloric  acid  are  insoluble  in  neutral  or  alkaline 
solutions.  Advantage  is  taken  of  these  and  other 
similar  facts  to  classify  substances  according  to  their 
reactions.  A  convenient  arrangement  for  purposes  of 
analysis  is  the  following  : 

CLASS  I.  Metals  whose  chlorides  are  insoluble  or 
difficultly  soluble  in  water.  This  class  includes  : 
Silver,  lead,  and  mercury  in  mercurous  salts. 

CLASS  II.  Metals  not  included  in  Class  I,  whose  sul- 
phides are,  however,  insoluble  in  dilute  hydro- 
chloric acid.  This  class  includes  :  Copper,  mer- 
cury (as  mercuric  salt),  bismuth,  antimony,  arsenic, 
and  tin. 

CLASS  III.  Metals  not  included  in  Classes  I  and  II, 
whose  sulphides  or  hydroxides  are,  however,  pre- 
cipitated by  ammonium  sulphide  and  ammonia. 
This  class  includes  :  Aluminium,  chromium,  nickel, 
cobalt,  iron,  zinc,  and  manganese. 

143 


144          sow  TO  ANALYZE  SUBSTANCES. 

CLASS  IV.  Metals  not  included  in  Classes  I,  II,  and 
III,  but  which  are  precipitated  by  ammonium 
chloride,  ammonia,  and  ammonium  carbonate 
This  class  includes  :  Barium, strontium,  and  calcium. 

CLASS  Y.  Metals  not  included  in  Classes  I,  II,  III, 
and  IY,  but  which  are  precipitated  by  disodium 
phosphate,  HNa2PO4,  ammonia,  and  ammonium 
chloride.  This  class  includes  :  Magnesium. 

CLASS  YI.  Metals  not  included  in  Classes  I,  II,  III, 
IY,  and  Y.  This  class  includes  :  Sodium,  potas- 
sium, and  ammonium. 

1.  Now,  suppose  you  have  a  substance  given  you 
for  analysis.     The  first  thing  to  do  is   to  get  the  sub- 
stance in  solution.     See  whether  it  dissolves  in  water. 
If  it  does  not,  try  dilute  hydrochloric  acid.  If  it  does  not 
dissolve  in  hydrochloric  acid,  try  nitric  acid ;  and  if  it 
does  not  dissolve  in  nitric  acid,  try  a  mixture  of  nitric 
and  hydrochloric  acids.     If  concentrated  acid  is  used, 
evaporate  to  dryness  on  a  water-bath  before  proceed- 
ing further.     Then  dissolve  in  water,  and  add  a  few 
drops  of  hydrochloric  acid.     If  a  precipitate  is  formed, 
continue  to  add  the  acid  drop  by  drop  until  a  precipi- 
tate is  no  longer  formed.     Filter  and  wash. 

What  may  this  precipitate  contain  ? 

2.  Pass  hydrogen  sulphide  through  the  filtrate  for 
some  time  and  let  stand.     Filter  and  wash. 

If  a  precipitate  is  formed,  what  may  it  contain  ? 

3.  Add  ammonia  and  then  ammonium  sulphide  to 
the  filtrate.     Filter  and  wash. 

If  a  precipitate  is  formed,  what  may  it  contain  ? 

4.  Add  ammonium  chloride,  ammonia,  and  ammo- 
nium carbonate  to  the  filtrate.     Filter  and  wash. 


EXAMPLES  FOR  PRACTICE.  145 

If  a  precipitate  is  formed,  what  may  it  contain  ? 
5.  Add  disodium  phosphate  to  the  filtrate.     Filter 
and  wash. 

•If  a  precipitate  is  formed,  what  may  it  contain? 
What  may  be  in  the  filtrate  ? 

EXAMPLES  FOE  PEACTICE. 

Before  attempting  anything  in  the  way  of  systematic 
analysis  it  will  be  wrell  to  experiment  in  a  more  general 
way,  with  the  object  of  determining  which  one  of  a 
given  list  of  substances  a  certain  specimen  is. 

The  list  below  contains  the  names  of  the  principal 
substances  with  which  you  have  thus  far  had  directly 
to  deal  in  your  work.  You  have  handled  them  and 
have  seen  how  they  act  toward  different  substances. 
Suppose  now  that  a  substance  is  given  you,  and  you 
know  simply  that  it  is  one  of  those  named  in  the  list, 
how  would  you  go  to  work  to  find  out  which  one  it  is  ? 
You  have  a  right  to  judge  by  anything  in  the  appear- 
ance or  in  the  conduct  of  the  substance.  If  you  reach 
a  conclusion,  see  whether  you  are  right  by  further 
experiments.  After  your  work  is  finished  write  out  a 
clear  account  of  what  you  have  done,  and  state  clearly 
your  reasons  for  the  conclusion  which  you  have  reached. 

For  example,  suppose  sodium  chloride  is  given 
you.  You  see  it  is  a  white  solid.  On  heating  it  in  a 
small  tube  you  see  that  it  does  not  melt,  but  it  breaks 
up  into  smaller  pieces  with  a  crackling  sound.  It  is 
soluble  in  water.  Hydrochloric  acid  causes  no  change 
when  added  to  a  little  of  the  solid.  Is  it  a  carbonate  ? 
Strong  sulphuric  acid  causes  evolution  of  a  gas.  Has 
this  an  odor  ?  How  does  it  appear  when  allowed  to 


146  HOW  TO  ANALYZE  SUBSTANCES. 

escape  into  the  air  ?  Is  it  nitric  acid  ?  Collect  some 
of  it  in  water.  How  does  this  solution  act  on  a  solu- 
tion of  silver  nitrate  ?  By  this  time  you  have  evidence 
that  you  are  dealing  with  a  chloride,  but  you  do  not 
yet  know  which  chloride  it  is.  It  cannot  be  ammonium 
chloride.  Why?  It  may  be  either  potassium  or 
sodium  chloride.  Try  a  small  piece  in  the  flame. 
What  color  ?  You  now  have  good  reasons  for  believ- 
ing that  the  substance  you  are  dealing  with  is  sodium 
chloride.  To  convince  yourself,  get  a  small  piece  of 
sodium  chloride  from  the  bottle  known  to  contain  it, 
and  make  a  series  of  parallel  experiments  with  this 
and  see  whether  you  get  exactly  the  same  results  that 
you  got  with  the  specimen  you  were  examining.  If 
not,  account  for  the  differences. 

By  careful  work  there  will  be  no  serious  difficulty 
in  determining  which  one  of  the  substances  in  the  list 
you  are  dealing  with. 

LIST  OF  SUBSTANCES  FOE    EXAMINATION. 

1.  Sugar.  13.  Ferrous  sulphate  (Cop- 

2.  Mercuric  oxide.  peras). 

3.  Calc-spar.  14.  Koll-sulphur. 

4.  Marble.  15.  Iron-filings. 

5.  Copper.  16.  Carbon  disulphide. 

6.  Hydrochloric  acid.        17.  Lead. 

7.  Nitric  acid.  18.  Potassium  chlorate. 

8.  Sulphuric  acid.  19.  Manganese  dioxide. 

9.  Zinc.  20.  Charcoal. 

10.  Tin.  21.  Calcium  sulphate 

11.  Sodium  sulphate.  (Gypsum). 

12.  Sodium  carbonate.         22.  Copper  oxide. 


STUDY  OF  CLASS  /.  147 

23.  Ammonium  chloride.     31.  Potassium  carbonate. 

24.  Calcium  oxide  (Quick-  32.  Potassium  nitrate. 

lime).  33.  Potassium  dichromate. 

25.  Sodium  nitrate.  34.  Ked  lead  (Minium). 

26.  Ammonium  nitrate.  35.  Lead  nitrate. 

27.  Sodium  chloride.  36.  Alum. 

28.  Potassium  bromide.  37.  White  arsenic. 

29.  Potassium  iodide.  38.  Antimony. 

30.  Iron  sulphide.  39.  Magnesium  sulphate. 

[The  teacher  will,  of  course,  select  the  substance 
and  give  it  to  the  pupil  without  any  suggestion  as  to 
what  it  is.  After  the  pupil  has  shown  that  he  can  tell 
with  certainty  which  substance  he  has,  some  simple 
mixtures  of  substances  selected  from  the  above  list 
may  next  be  given  for  examination.  Thus  charcoal 
and  copper  oxide ;  zinc  and  tin ;  mercuric  oxide  and 
iron-filings ;  etc.,  etc.] 

STUDY  OF  CLASS  I. 
EXPERIMENT  195. 

1.  Prepare  dilute  solutions  of  silver  nitrate,  AgNO3, 
lead  nitrate,  Pb(NO3)2,  and  mercurous  nitrate,  HgNO3. 

2.  Add  to  a  small  quantity  of  each  separately  in 
test-tubes  a  little  hydrochloric  acid. 

What  is  formed? 

3.  Heat  each  tube  with  its  contents,  and  then  let  it 
cool. 

What  difference  do  you  observe  ? 

4.  After  cooling,  add  a  little  ammonia  to  the  con- 
tents of  each  tube. 

What  takes  place  in  each  case  ? 


148  HOW  TO  ANALYZE  SUBSTANCES. 

How  could  you  distinguish  between  silver,  lead,  and 
mercury  ? 

5.  Mix  the   solutions  of  silver  nitrate,  lead  nitrate, 
and  mercurous  nitrate,  and  to  a  little  of  the  mixture 
in  a  test-tube  add  water  and  then  hydrochloric  acid  as 
long  as  it  causes  the  formation  of  a  precipitate.    Heat 
to  boiling.     Filter  rapidly  and  wash  with  hot  water. 

What  is  in  the  nitrate,  and  what  is  on  the  filter  ? 

6.  Let  the  filtrate  cool. 

What  evidence  have  you   that   there   is   anything 
present  in  it  ? 

7.  Add  sulphuric  acid  to  a  little  of  the  liquid. 

8.  Add  hydrogen  sulphide  to  a  little  of  the  liquid. 

9.  Pour  ammonia  on  the  filter,  and  wash  out  with 
water.     Then  add  nitric  acid  to  the  filtrate. 

What  evidence  do  you  get  of  the  presence  of  silver 
and  of  mercury  ? 

STUDY  OF   CLASS  II. 
EXPERIMENT  196. 

1.  Prepare  dilute  solutions  of  copper  sulphate,  of 
mercuric  chloride,  of  arsenic  trioxide  in  hydrochloric 
acid,  and  of  tin  in  hydrochloric  acid.     [Bismuth  and 
antimony  are  omitted,  as  their  presence  gives  rise  to 
difficulties  hard  to  deal  with  intelligently  at  this  stage.] 
Add  a  little  hydrochloric  acid  to  the  solutions  of  cop- 
per sulphate  and  of  mercuric  chloride. 

2.  Pass  hydrogen  sulphide  through  a  small  quan- 
tity of  each  of  the  solutions. 

What    takes    place  ?      What    are    the    substances 
formed  ? 

3.  Fiiter  and  wash.     Treat  each  precipitate  with  a 
solution  of  yellow  ammonium  sulphide, 


STUDY  OF  CLASS  II.  149 

What  takes  place?  Add  dilute  sulphuric  acid  to 
the  filtrates. 

What  takes  place  ? 

4.  Treat  the  precipitates  obtained  from  the  copper 
and  the  mercury  salts  with  concentrated  warm  nitric 
acid. 

Does  either  one  dissolve  easily  ?  What  is  the  color 
of  the  solution  ? 

5.  Treat  a  little  of  the  solution  obtained  in  4.  with 
ammonia. 

What  is  the  result?  How  can  you  detect  the  pres- 
ence of  copper? 

6.  Treat  with  a  mixture  of  nitric  and  hydrochloric 
acid  the  precipitate  which  is  not  readily  dissolved  by 
nitric  acid   alone.     Evaporate  the  acid.     Add  water, 
and  then  a  solution  of  stannous  chloride.    (See  Experi- 
ment 175.) 

What  other  compound  of  tin  and  chlorine  is  there  ? 

[When  stannous  chloride,  SnCl2,  acts  upon  mercuric 
chloride,  HgCl2,  the  former  takes  a  part  or  all  of  the 
chlorine  from  the  latter,  forming  either  mercurous 
chloride,  HgCl,  or  mercury,  thus  : 

(a)    2HgCl2  +  SnCl2  =  2HgCl  +  SnCl4 ; 
(6)     2HgCl  +  SnCl2  =  2Hg  +  SnCl4.] 

7.  Treat  the  precipitate  obtained  in  the  case  ot  the 
arsenic  with    4-5   cc.   of   a   concentrated  solution  of 
ammonium  carbonate.     To  the  solution  add  hydro- 
chloric acid  and  a  few  crystals  of  potassium  chlorate, 
and  boil  until  chlorine  is  no  longer  given  off.     Add 
ammonia,  ammonium  chloride,  and   magnesium   sul- 
phate to  the  solution.    The  precipitate  is  ammonium 
magnesium  arsenate, 


150  HOW  TO  ANALYZE  SUBSTANCES. 

8.  Dissolve  the  tin  precipitate  in  concentrated  hydro- 
chloric acid.   Dilute  and  add  a  few  small  pieces  of  zinc. 
Dissolve  in  hydrochloric  acid  the  tin  which  separates. 

What  will  the  solution  thus  obtained  contain  ? 

What  should  take  place  on  adding  the  solution  to  a 
solution  of  mercuric  chloride  ?  Try  it. 

Mix  the  solutions  prepared  in  1.,  and  proceed  as 
follows : 

9.  Pass  hydrogen  sulphide ;  filter ;  wash  ;  treat  the 
precipitate  with  ammonium  sulphide ;  filter ;  wash. 

What  is  now  in  solution  ? 
What  is  in  the  filter  ? 

10.  Treat  the  solution  with  dilute  sulphuric  acid. 
Filter ;   wash.      Treat  the  precipitate  thus  obtained 
with  concentrated  ammonium-carbonate  solution.   Fil- 
ter ;  wash.    Treat  the  solution  as  directed  in  7.,  and 
the  precipitate  as  in  8. 

11.  Treat  with  warm  concentrated  nitric  and  hydro- 
chloric acids  the  precipitate  left  after  treating  with 
ammonium  sulphide  as  in  9.    Test  for  copper  as  in  5., 
and  for  mercury  as  in  6. 

STUDY  OF  CLASS   III:  ALUMINIUM. 
EXPERIMENT  197. 

1.  Prepare  a  solution  of  ordinary  alum.     [What  is 
ordinary  alum  ?] 

2.  Add  to  this  solution  ammonia,  ammonium  chlo- 
ride,  and    ammonium    sulphide.     Filter    and   wash. 
Treat   the   precipitate    with  hydrochloric   acid ;    and 
then  treat  the  solution  thus  obtained  with  ammonia. 

[Aluminium  does  not  form  a  sulphide ;  but  the  hy- 
droxide, A1(OH)3,  is  formed  when  ammonia,  ammoni- 


STUDY  OF  CLASS  III.  151 

um  chloride,  and  ammonium  sulphide  are  added  to  a 
solution  of  its  salts.  When  the  hydroxide  is  treated 
with  hydrochloric  acid  it  is  converted  into  the  chlo- 
ride, A1C13 ,  which  dissolves ;  and  when  the  solution 
of  the  chloride  is  treated  with  ammonia  the  hydroxide 
is  precipitated : 

A101,  +  3NH3  +  3H20  =  Al(OH),  +  3NH4C1.] 

3.  Dissolve  the  precipitate  of  aluminium  hydroxide, 
A1(OH)3,  in  as  little  hydrochloric  acid  as  possible, 
and  add  a  cold  solution  of  sodium  hydroxide.     Boil 
the  solution  thus  obtained. 

4.  After   cooling,    slowly  add    dilute   hydrochloric 
acid.     When  the  alkali  is  neutralized,  aluminium  hy- 
droxide, A1(OH)3,  will  be  precipitated.     It  will  dis- 
solve  on  the  addition  of  more  acid ;   and  from  the 
solution  thus  obtained  the  hydroxide  can  be  precipi- 
tated by  a  solution  of  ammonia. 

STUDY  OF  CLASS  III:  CHBOMIUlf. 
EXPERIMENT  198. 

1.  Prepare  a  solution  of  chromic  chloride,  CrCl3, 
as  directed  in  Experiment  188.     Explain  the  reaction 
involved  and  write  the  equations. 

2.  Treat  the  solution  of  chromic  chloride  as  under 
2.  and  3.,  Experiment  197,  and  note  the  differences. 

How  could  you  distinguish  between  aluminium  and 
chromium  ? 

STUDY  OF  CLASS  III:  IEON. 

EXPERIMENT  199. 

1.  Prepare  a  solution  containing  ferrous  chloride, 
(See  Experiment  180.) 


152  HOW  TO  ANALYZE  SUBSTANCES. 

2.  Convert  a  part  of  this  into  ferric  chloride.     (See 
Experiment  180.) 

3.  Treat  each  of  these  solutions  with  ammonia  until 
neutral  and  then  with  ammonium  sulphide. 

[The  precipitate  is  the  same  in  both  cases,  and  the 
action  is  represented  thus  : 

Fed,  +  (NH4)aS  =  FeS    +2NH4C1; 
2FeCl,  -f  3(NH4)aS  =  2FeS  +  6NH4C1  +  S.] 

4.  Dissolve  the  precipitate  in  hydrochloric  acid : 

FeS  +  2HC1  =  FeCla  +  H2S. 

5.  Convert  the  ferrous  into  ferric  chloride.     (See 
Experiment  180.) 

6.  Treat  with   ammonium    chloride   and  ammonia. 
Filter  and  wash.     Treat  the  precipitate  as  directed 
under  3.,  Experiment  197. 

What  differences   are    there    between   aluminium, 
chromium,  and  iron  ? 

7.  Filter ;  dissolve  the  precipitate  in  dilute  hydro- 
chloric acid ;  and  treat  with  a  solution  of  potassium 
ferrocyanide,  K4Fe(CN)6 . 

The   precipitate  formed  in   this   case  is  Prussian 
blue,  or  ferric  ferrocyanide. 

STUDY  OF  CLASS  III:  ZINC. 
EXPERIMENT  200. 

1.  Prepare  a  dilute  solution  of  zinc  sulphate. 

2.  Treat  with   ammonia  and  ammonium   sulphide. 
What  is  the  color  of  the  precipitate  ?     Its  composi- 
tion is  represented  by  the  formula  ZnS. 

3.  Dissolve  in  dilute  hydrochloric  acid  : 

s  ZnCl,  +  H,8, 


STUDY  OF  CLASS  III.  153 

4.  Boil  the  solution  thoroughly  to  remove  all  hy- 
drogen sulphide,  and  then  treat  with  ammonium  chlo- 
ride and  ammonia.     Is  a  precipitate  formed  ? 

5.  Add  enough  hydrochloric  acid  to  give  the  solu- 
tion an  acid  reaction,  and  then  add  sodium  acetate, 
NaC,H30, : 

ZnCl,  +  2NaC,H3O,  =  2NaCl  +  Zn(C2H3O2)2. 

6.  Pass   hydrogen  sulphide  through  the   solution. 
The  white  precipitate  is  zinc  sulphide,  ZnS. 

Is  the  solution  acid  ?  If  so,  with  what  acid  ?  Is 
zinc  sulphide  precipitated  in  the  presence  of  free 
hydrochloric  acid  ? 

What  differences  are  there  between  aluminium, 
chromium,  iron,  and  zinc  ?  How  could  they  be  sepa- 
rated and  detected  if  present  in  the  same  solution  ? 

[It  will  be  well  for  the  teacher  to  prepare  solutions 
containing  two  or  more  members  of  Class  III,  and  to 
give  them  to  the  pupil  for  analysis.] 

STUDY  OF   CLASS  III:   MANGANESE. 
EXPERIMENT  201. 

1.  Treat  a  little  manganese  dioxide  in  a  test-tube 
with  strong  hydrochloric  acid.    Boil,  dilute,  and  filter. 

What  have  you  in  solution  ? 

2.  Treat  as  under  2.,  3.,  4.,  5.,  6.,  in  the  preceding 
Experiment. 

In  what  respects  do  manganese  and  zinc  differ  ? 

3.  To  the  solution  through  which  you   have  just 
passed   hydrogen    sulphide   add   sodium   hydroxide, 
NaOH,  until  most  of  the  acetic  acid  is  neutralized ; 
heat  gently  and  add  bromine-water,     Let  the  liquid 
stand  for  au-hour, 


154  HO W  TO  ANALYZE  SUBSTANCES. 

What  takes  place  ?  [The  composition  of  the  pre- 
cipitate is  represented  by  the  formula  Mn(OH)4.] 

How  could  you  separate  manganese  from  the  other 
members  of  the  group  ? 

STUDY  OF  CLASS  III. 
EXPERIMENT  202. 

1.  Mix  dilute  solutions  of  alum,  chromic  chloride 
(prepared  as  in  Experiment  188,  1.),  ferrous  chloride 
(prepared  as  in  Experiment  104),  zinc  sulphate,  and 
manganous  chloride. 

2.  Treat  with  ammonia,  ammonium  chloride,  and 
ammonium  sulphide.     Filter  and  wash. 

3.  Treat  the  precipitate  with   dilute   hydrochloric 
acid;   treat  with  concentrated  nitric  acid  to  convert 
ferrous  chloride  into  ferric  chloride  (Experiment  180) ; 
and  then  treat  the  solution  thus  obtained  with  am- 
monium chloride  and  ammonia. 

What  have  you  in  the  precipitate  ?     (Call  this  A.) 
What  in  the  solution  ?     (Call  this  B.) 

4.  Dissolve  the  precipitate  in  a  little  dilute  hydro- 
chloric acid,  and  add  a  cold  solution  of  sodium  hy- 
droxide, more  than  enough  to  neutralize  the  hydro- 
chloric   acid.      Filter ;    dissolve    the    precipitate    IM 
hydrochloric  acid  ;  and  treat  with  a  solution  of  po- 
tassium   ferrocyanide,  K4Fe(CN)6.     (See  Experiment 
199,  7.)    Boil  the  nitrate  from  the  precipitate  of  ferric 
hydroxide.     What  is  precipitated  ?     Treat  the  nitrate 
as  directed  in  Experiment  197,  4. 

5.  Treat   the   solution   B   (see  under  3.  above)  as 
directed  under  5.  and  6.,  Experiment  200 ;  and  under 
3.,  Experiment  201. 

Examine  mixtures  containing  members  of  Class  III. 


STUDY  OF  CLASS  IV.  155 

STUDY   OF  CLASS  IV:  CALCIUM. 
EXPERIMENT  203. 

1.  Prepare  a  solution  of  calcium  chloride  by  dis- 
solving a  little  calcium  carbonate  (marble)  in  hydro- 
chloric acid.     What  is  the  reaction  ? 

2.  Treat  with  ammonium  chloride,  ammonia,  and 
ammonium  carbonate,  (NH4),CO,.     Filter  and  wash. 

What  takes  place  ?     Write  the  equation. 

3.  Dissolve  the  precipitate  in  dilute  hydrochloric 
acid.     Treat  a  small  part  of  this  solution  with  a  solu- 
tion of  calcium  sulphate  in  water.     Does  a  solution  of 
calcium  chloride  give  a  precipitate  when  treated  with 
a  solution  of  calcium  sulphate  ? 

Treat  another  small  part  with  ammonia  and  am- 
monium oxalate,  (NH4)aCaO4»  The  precipitate  is  cal- 
cium oxalate,  CaC2O4. 

STUDY   OF   CLASS  IV:  BAEIUM. 
EXPERIMENT  204. 

1.  Prepare  a  dilute  solution  of  barium  chloride  in 
water. 

2.  Treat  as  directed  under  2.,  preceding  Experi- 
ment. 

3.  Dissolve  the  precipitate  in  dilute  hydrochloric 
acid.     Treat  a  small  part  of  this  solution  with  a  solu- 
tion of  calcium  sulphate  in  water. 

What  difference  do  you  notice  between  the  conduct 
of  calcium  and  that  of  barium  ? 

How  could  you  detect  barium  and  calcium  when 
present  in  the  same  solution  ? 


HOW  TO  ANALYZE  SUBSTANCES. 

Mix  the  solutions  of  barium  and  calcium  chlorides, 
and  try  the  reactions  described  in  Experiments  203 
and  204. 

STUDY  OF  CLASS  V:  MAGNESIUM. 
EXPERIMENT  205. 

1.  Prepare  a  dilute  solution  of  magnesium  sulphate 
in  water. 

2.  Add  ammonium  chloride,  ammonia,  and  disodium 
phosphate,  HNa2PO4. 

The  precipitate  formed  is  ammonium  magnesium 
phosphate,  NH4MgPO4.  What  similar  precipitate  has 
already  been  obtained  ?  (See  Experiment  196,  7.) 

3.  Mix  solutions  of  barium  chloride,  calcium  chlo- 
ride, and  magnesium  chloride ;  and  see  whether  you 
can  detect  the  three  metals  by  means  of  the  reactions 
described  in  Experiments  203,  204,  and  205. 

STUDY  OF  CLASS  YI. 
EXPERIMENT  206. 

1.  Potassium  can  be  detected  by  means  of  the  color 
it  gives  to  a  flame  (see  Experiment  149) ;  and  also  by 
the  fact  that  when  platinic  chloride,  PtCl4 ,  is  added  to 
a  solution  of  a  potassium  salt,  the  salt  K2PtCl8  is  pre- 
cipitated.    (See  Experiment  148.)     Try  this. 

2.  Sodium  is  detected  by  means  of  the  flame-reac- 
tion.    (See  Experiment  149.) 

3.  Ammonium  salts  are  detected  by  adding  an  alkali 
and  warming,  when  ammonia  gas  is  given  off,  and  this 
is  easily  recognized. 


SYMBOLS  AND  ATOMIC  WEIGHTS  OF  THE 
ELEMENTS. 


Atomic 

Atomic 

Element.          Symbol.  Weight. 

Element.          Symbol.  Weight. 

Aluminium 

Al 

27. 

Mercury 

Hg 

200. 

Antimony 

Sb 

120. 

Molybdenum 

Mo 

95.9 

Arsenic 

As 

75. 

Nickel 

Ni 

58.6 

Barium 

Ba 

137. 

Nitrogen 

N 

14. 

Bismuth 

Bi 

208. 

Osmium 

Os 

191. 

Boron 

B 

11. 

Oxygen 

0 

16. 

Bromine 

Br 

80.     Palladium 

Pd 

106.2 

Cadmium 
Caesium 

Cd 

Cs 

112.    |  Phosphorus 
133.     Platinum 

P 
Pt 

31. 
194.3 

Calcium 

Ca 

40. 

Potassium 

K 

39. 

Carbon 

C 

12. 

Rhodium 

Eh 

104.1 

Cerium 

Ce 

141.5  Eubidium 

Eb 

85. 

Chlorine 

Cl 

35.4  Kuthenium 

Eu 

103.5 

Chromium 

Cr 

52.3  Scandium 

Sc 

44. 

Cobalt 

Co 

58.7  Selenium 

Se 

79. 

Columbium 

Cb 

93.7  Silicon 

Si 

28. 

Copper 

Cu 

63.2  Silver 

Ag 

108. 

Didymium 

Di 

145. 

Sodium 

Na 

23. 

Erbium 

E 

166. 

Strontium 

Sr 

87.5 

Fluorine 

F 

19. 

Sulphur 

S 

32. 

Gallium 

Ga 

69.9 

Tantalum 

Ta 

182. 

Germanium 

Ge 

72.3 

Tellurium 

Te 

125. 

Gluciuum 

Gl 

9. 

Thallium 

Tl 

204. 

Gold 

Au 

196.7 

Thorium 

Th 

232. 

Hydrogen 

H 

1. 

Tin 

Sn 

118. 

Indium 

In 

113.7 

Titanium 

Ti 

48. 

Iodine 

I 

127. 

Tungsten 

W 

184. 

Iridium 

Ir 

192.5 

Uranium 

U 

240. 

Iron 

Fe 

56. 

Vanadium 

Y 

51.1 

Lanthanum 

La 

138.5 

Ytterbium 

Yt 

173.2 

Lead 

Pb 

207. 

Yttrium 

Y 

89. 

Lithium 

Li 

7. 

Zinc 

Zn 

65. 

Magnesium 

Mg 

24. 

Zirconium 

Zr 

90.4 

Manganese 

Mn 

55. 

157 


Poand.       Ounces.     Drams. 


WEIGHTS  AND  MEASURES. 

Troy  or  Apothecaries'  Weight. 
Scruples.         Grains. 


-<       


12     =  96     = 

1     =     8     = 

1     = 


288 

24 

3 

1 


5760 

480 

60 

20 

1 


Avoirdupois  Weight. 
Pound.       Ounces.  Drams.  Grains. 

1     =     16      =      256      =      7000 
1      =        16      =       437.5 

1      =         27.343      = 

Imperial  Measure. 
Gallon.      Pints.          Fluid  Ounces.  Fluid  Drams. 

1     =     8=        160        =         1280 
1      ==          20        =  160 

1        =  8 

1 

METKIC  SYSTEM. 
Measures  of  Length. 

English  Inches. 

1  Millimetre  =  .03937 
1  Centimetre  =  .39371 
1  Decimetre  =  3.93710 


Grams. 

372.96 
31.08 
3.885 
1.295 
0.0647 

Grams. 
453.25 
28.328 
1.77 


Minims. 

=  76800 

=  9600 

=  480 

=  60 


1  Metre 


=    39.37100 


Measures  of  Capacity. 


1  Cubic  Centimetre 
1  Centilitre  (10  cc.) 
1  Decilitre  (100  cc.) 
1  Litre 


English  Imperial  Measure. 
Pint.      F.  Oz.    F.  Dram.     Min. 


0 

0 

3 

15 


16.3 
43 
2 
43 


Measures  of  Weight. 

English  Grains.  Avoirdupois. 

1  Gram         =         15.4323        Pounds.       Oz.       Dms. 
1  Kilogram  ~     15432.348  =2  35 

158 


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